WEIGHING BULLETS TO REDUCE VELOCITY VARIATION AND IMPROVE ACCURACY

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joeb33050 posted this 2 weeks ago

 

 

WEIGHING BULLETS TO REDUCE VELOCITY VARIATION AND IMPROVE ACCURACY

 

223, 5.5 gr Titegroup, 40 gr bullet, 2063 fps, 53 gr bullet, 1784 fps, delta fps/gr, 21.5

 

223, 8.5 gr Titegroup, 40 gr bullet, 2678 fps, 53 gr bullet, 2374 fps, delta fps/gr, 23.4

 

22-250, 5.5 gr Titegroup, 40 gr bullet, 1857 fps, 53 gr bullet, 1622 fps, delta fps/gr, 18.1

 

22-250, 8.5 gr Titegroup, 40 gr bullet, 2418 fps, 53 gr bullet, 2137 fps, delta fps/gr, 21.6

 

The largest delta fps/gr of bullet weight is 23.4; a bullet weighing 1 grain more than another would go 23.4 fps slower.

 

Weighing, segregating, loading and shooting bullets into .1 grain classes reduces delta fps to 2.34 fps.

 

In .5 gr classes, delta fps is 14.0 fps.

 

Weighing bullets and segregating them into small classes won’t improve accuracy.

 

joe b.

 

 

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RicinYakima posted this 2 weeks ago

"Weighing bullets and segregating them into small classes won’t improve accuracy.

 

joe b."

 

I agree that is true PROVIDED the bullets are screened visually first. After our tests last year, I still weigh bullets only because I am running out of linotype and having to blend my own alloys out of foundry type and WW's. About 5% of the bullets will have small voids in the base or rounded driving bands compared to linotype that has almost none.

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Larry Gibson posted this 2 weeks ago

I've found absolutely no correlation between accuracy and any SD or ES measurement of 10 shot groups.  There is usually as much variation if not more than is mentioned between the SD and ES of identical loads tested with as many as 5 test strings. 

 

I do weight sort in .1 gr segregations with my match and HV cast bullets; the 314299 (188 gr) and the NOE 30 XCB (158 gr) .  I also am pretty anal about rejecting any bullet with any kind of visual flaw.  These weighed bullets that pass visual screening are sorted into .1 gr tubs. Out of a 400 - 600 bullet batch about 17 - 20% will be sorted out because of visual defect or they weigh to light or to heavy (usually only a few are to heavy.  Most will weight sort within .2 to .3 gr +/- of each other which are shooters.  Of the .5 to .6 gr spread I only use the top half of the 314299s in CBA Military Rifle matches or the top half of the 30 XCBs for really high velocity loads (2600 - 2900+ fps).  The bottom half of the shooters I use as foulers, sighters and practice. 

 

I have shot enough of each to know that the kind of weight sorting I do makes a difference.  The last couple years I've taken 1st at every Military match I shot in except one.  That one I didn't have any of my weight sorted match shooters left so I went with the low weight end of the foulers and sighters......ended up with too many uncalled 9s and a couple 8s, especially at 200 yards.  When you are running cast bullets at 2600 - 2900 fps you are pushing them hard.  With the match shooter 30 XCBs at 2900 fps my rifle holds 1 1/2 or better moa at 300 yards. with the fouler/sighter shooters that opens to 1 1/2 to 2 moa.

 

I've seen the results of not weight sorting too many times to think weight sorting doesn't make a difference \.

 

LMG

I have found that the best and most consistent accuracy comes

Concealment is not cover.........

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joeb33050 posted this 2 weeks ago

I have shot enough of each to know that the kind of weight sorting I do makes a difference.  

Larry, I recognize your need to opine, now show us your data. 

joe b.

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Larry Gibson posted this 2 weeks ago

Joe

 

Here's the "data" I pay attention to, which in the end is what I believe really counts;

I've won 6 matches with weight sorted bullets and lost one with non-weight sorted bullets.   The 314299 in a CBA Military rifle match shooting for score;

 

Here's the 30 XCB at 2900+ fps shooting for score;

 

 

LMG

Concealment is not cover.........

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Larry Gibson posted this 2 weeks ago

Joe

Here's the results of an extended test of the 314299 load demonstrating the need to really use a large enough sample;

Average Velocity, ES and SD Variation

 I was testing a new (to me) NOE bullet in my M39 Finn Mosin-Nagant 7.62x54R rifle I use in CBA Military Rifle matches so I thought, since I was shooting five 10 shot test strings of the same load, I would chronograph each 10 shot test string to not the subtle differences in the average velocity, ES and SDs of the same load.  Since the CBA matches I attend are for group and for score (using the 100 and 200 yard reduced 600 yard NRA HP target) I shot three of the test strings at 100 yards to also test for accuracy and to confirm the 100 yard zero.  I then would shoot the two remaining test strings at 200 yards to confirm the zero. 

I had cast the NOE bullets using a 311-205 four cavity aluminum mould out of Lyman #2 alloy.  The bullets were very uniform with few rejections during visual inspection and weight sorting.  The bullets dropped just over .313 on the bands and .302+ on the nose.  I seated and crimped the Hornady GCs and lubed them with 2500+ in a Lyman 450 with .314 H&I die. Fully dressed they weighed in right at 200 grains.  I loaded them in NS’d Norma cases over 28.5 gr of milsurp 4895 with a 1 gr dacron filler.  WLR primers were used.  That is the match load I use with the Lyman 314299 which has won me two state championships and numerous matches.  I was hoping the NOE bullet would shoot as well as the Lyman and it did.

 Many times we see posted on forum a velocity given as XXXX fps with many, if not most, not understanding that chronographed figure is not an absolute.  There always will be some variance in the average fps, the ES and the SD of any test of a lot of ammunition.  What the variance can be is not only dependent on the quality of the ammunition but also on the number of shots in the test strings.  I consider 3 shot tests as only giving an idea of what may be expected.  A 5 shot test gives a better idea but still leaves considerable room for error.  The 10 shot test is standard but even that gives an optimistic average, ES and SD fps.

The five 10 shot results;

 Average fps,  ES fps,  SD fps

1813,  34,  12

 1817,  25,  7

1812,  39,  10

1826,  42,  13

1821,  41,  13

We see here a total difference in average velocity between each test string of only 13 fps.  The ES varied 22 fps and the SD varied, between strings, 6 fps.  All of which indicates a very consistent load even considering the differences.  However, to get a much better understanding lets look at the figures for the entire 50 shot test. 

For the entire 50 shot test the average velocity was 1818 fps.  The ES was 52 fps and the SD was 17 fps.  Some would not consider those figures to be good yet given the winning record of the load it has proven to be a very good load.  Bottom line is to actually have the best idea of a loads potential it pays to test a sufficiently large sample.  The smallest 10 shot group was not with the test that gave the smallest SD and ES. This is why I don’t give much credence to less than a 10 shot test and really prefer at least three 10 shot back to back tests to confirm probable ballistics and accuracy potential. 

 

LMG

Concealment is not cover.........

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TRKakaCatWhisperer posted this 2 weeks ago

Let me stir the pot.  The single most important thing that has improved the quality of my bullets is to have weighed bullets as they are cast.  That has directly indicated behaviors (temperature, timing, techniques) that cause variation (in more than just weight).

 

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Larry Gibson posted this 2 weeks ago

Joe

 

I am not arguing with your data at all.  I'm just saying that your conclusion of "Weighing bullets and segregating them into small classes won’t improve accuracy" is basically incorrect because the data is only from one half of the equation that affects accuracy.  That half being measurement and data derived from the internal ballistics.  The half of the equation not addressed is the external ballistics.  You present no data referencing that half.  Your conclusion is only based on the first half, thus the error. 

 

Here is further information on how I weight sort and with some test data demonstrating the results on target which accounts for both internal and external ballistic affect on the bullets.

It depends on the weight of the cast bullet to begin with. Most weight sort thinking those bullets that weigh the same or with a +/- will shoot the best. I've learned that while that method of selection will give better accuracy it will not give "the best". As I weigh each bullet I visually inspect the bullets first. Any visual defect, no matter how small, is cause for rejection. I then weight sort to eliminate those very light bullets that passed the visual inspection but obviously have a void inside. I then put the bullets into small plastic bowls of .1 gr increments.

I'll explain with 7mm to 32 caliber bullets of 150 to 220 gr as an example. Many who weight sort will kind of "graph" the bullets out by lining them up in tenth grain increments that are consecutively numbered and straight across the bottom. What you end up with is a "bell curve" shape of bullets. The curve starts out curving up, peaks out and then curves back down almost the same as it went up. The majority of the bullets in the curve will have a 1 to 1.5 grain difference in weight. There will be some that are much lighter and a few heavier. That is what you get with "good" cast bullets.

Using a quality alloy that will cast excellent bullets is also paramount. This is why straight linotype and #2 alloy are most often used. They give excellent and uniform fill out, consistency of weight with fewer defects. Some batches of COWWs will also if the antimony and tin percentages are sufficient and balanced. Alloys in these smaller caliber bullets that give a lot of shrinkage will never cast "excellent" bullets no matter how good they look. The reason is we cannot control the shrinkage and where it occurs on each bullet. Slight shrinkages that are in different places on the bullet are undetectable by visual or even precise measurement and they mean a slightly unbalanced bullet. Might not seem like much but at higher RPM and/or at longer ranges of 200 yards and beyond it is readily detectable on target by enlarged groups and poorer accuracy. Complete fill out in the mould and minimal shrinkage is needed for a quality cast bullet that will give the best accuracy.

Weight sorting the visual inspection passed bullets with "excellent cast" bullets gives a weight sorted curve that rises sharply and then levels off with several weights (three or four of .1 grain increment) having about the same number of bullets. The curve then falls sharply to just a few heavier bullets. There is no downward "curve".

When I got the 4 cavity NOE 30 XCB mould I ran this test with Lyman #2 alloy;

I cast 531 bullets

1.9% were rejected for visual defects

8.6% weighed less than 157.7 gr (some as much as 2 gr less that obviously had internal voids I could not detect through visual inspection)

3% weighed 157.8 gr

4.5% weighed 157.9 gr

5.9% weighed 158 gr

18.7% weighed 158.1 gr

19.3% weighed 158.2 gr

21.6% weighed 158.3 gr

14.7% weighed 158.4 gr

1.8% weighed 158.5 gr.

I then loaded 10 shots of each increment (157.8 gr to 158.5 gr) to test at 300 yards.

Test rifle was my 30x60 XCB. The NOE bullets weight 164 gr +/- when fully dressed and were loaded over 53 gr of AA4350 which runs 2900+ fps out of that rifle. The incremental test loads were fired consecutive by weight with the barrel cooled, cleaned and then fouled with 2 fouling shots prior to the next increment test. The results were then graphed out for a simple visual comparison.

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We see the lighter weight 157.8 and 157.9 gr bullets were not as accurate. The lighter weight bullets giving indication to probable incomplete and inconsistent fill out and/or shrinkage or that they have small void(s) in them.  The "heavy" end of the bullets (158.0 through 158.5 gr) gave consistent accuracy (precision) at very close to moa at 300 yards. I have run this test several times and with cast bullets in the 150 - 180 gr weight range I select the heavy end of the weight sorted bullets +/- .2 to .25 gr. With this weight range I use the 157.8 and 157.9 gr bullets for foulers and the 158.0158.1 bullets for sighters. The 158.2 through 158.5 are then used in matches and other tests where precision is measured.  For the best accuracy at this level of high velocity the top half (158.3 to 158.5 gr) of those selected bullets almost always give the best results, particularly at 200 and 300 yards.

With other weight ranges I like wise run a similar weight sort test and now select the heavy end of the match selected weight sorted bullets for accuracy/precision use.

 

Concealment is not cover.........

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TRKakaCatWhisperer posted this 2 weeks ago

I use a filter for most posts.  "This worked for me ..." is the PASS filter - I read them carefully.  "Something won't work" gets translated into "I haven't figured it out yet.

 

 

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joeb33050 posted this 2 weeks ago

Larry Gibson uses a lotta words to say little to nothing about the topic. Larry's data sums to two ten shot 300 yard groups at ~ 4", the others ~ 3". His sample size is 1. The data is meaningless. Larry, tell us about groups with same weight bullets vs groups with varied weight bullets-that's the subject.

TRK? 

joe b.

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Larry Gibson posted this 2 weeks ago

Respectfully disagree joe.  The topic of my posts was disagreement with your blanket conclusion at the end of your opening post of; "Weighing bullets and segregating them into small classes won’t improve accuracy" .  Your study of data/statistics is commendable but as I stated in my 1st post the data you presented only related to internal ballistics.  You mention nothing about the effect on accuracy of external ballistics (flight to the target).  You drew a conclusion based on only half of the equation. Point being you can have the most uniform data (fps, ES and SDs) or the smallest "delta" yet still have very poor accuracy. 

By ignoring the external ballistic phase in your analysis you are also ignoring the fact that a difference in weight between bullets indicates a potential balance problem within the cast bullet.  That balance problem becomes apparent not in fps figures derived from chronograph data but from on target performance because it only affects the bullet in flight. Keeping cast bullets as close to the same weight is as essential to achieving the best accuracy because it helps ensure a uniformly balanced bullet, or at least as uniform as we can cast one.  If there is a .5 gr difference in weight (on a 164 gr cast bullet) we do not know where in or on the bullet that difference is if there is no sign of a defect.  That difference in bullet weight is an imbalance.  That imbalance will not show any measurable effect in chronograph data.  The imbalance will only show its effect during the bullets flight.   Weight sorting is tantamount to the same principle as is keeping bullet jacket thickness uniform to benchrest competitors.  Imbalances in bullets and their adverse affect during flight is why we shoot "groups" instead of all shots going into the same hole.  The smaller the imbalances in the bullet during flightthe smaller the group.

As to sample size joe., let's take a look at the first sample line from your 1st post;

"223, 5.5 gr Titegroup, 40 gr bullet, 2063 fps, 53 gr bullet, 1784 fps, delta fps/gr, 21.5"

What was the sample size for each velocity?  Was the velocities listed an average?  What was the ES of each?  Did the ESs overlap between the two velocities?

If each velocity was more than one shot was that listed velocity only from one test string?  Of how many shots in the test strings?  I posted a test demonstrating the variation of average velocity, ES and SD of five tests of the same identical load with 10 shots in each test string.  That demonstrated the variation that can occur between the average velocity, the ES and the SD of different tests of the same load.  Did you fire more than one test string of each load?  Do we know what the variation was of the two loads if you fired more than one test per load? 

Is the "Delta" figure based simply on the difference between just the two unquantified samples? 

Now I may be just "opining" and have "little or nothing to say" about my "meaningless" data but I have presented actual on target data demonstrating that weight sorting can be beneficial to accuracy if done and used correctly.  So please, you have any actual "on target data" to refute that and substantiate your conclusion of; "Weighing bullets and segregating them into small classes won’t improve accuracy"  can you post that?  Also if you can show us "data' that weight variation in cast bullets do not create imbalances and that such imbalances do not adversely affect the bullets accuracy in flight I would be glad to see that?

LMG

 

Concealment is not cover.........

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joeb33050 posted this 2 weeks ago

Larry, I'd be happy to send you, or anyone, all the data. Just ask.

joeb33050@yahoo.com

 

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OU812 posted this 2 weeks ago

Thanks for listing your chroni results.

WEIGHING BULLETS TO REDUCE VELOCITY VARIATION AND IMPROVE ACCURACY

 

 

 

223, 5.5 gr Titegroup, 40 gr bullet, 2063 fps, 53 gr bullet, 1784 fps, delta fps/gr, 21.5

 

 

 

223, 8.5 gr Titegroup, 40 gr bullet, 2678 fps, 53 gr bullet, 2374 fps, delta fps/gr, 23.4

 

 

 

22-250, 5.5 gr Titegroup, 40 gr bullet, 1857 fps, 53 gr bullet, 1622 fps, delta fps/gr, 18.1

 

 

 

22-250, 8.5 gr Titegroup, 40 gr bullet, 2418 fps, 53 gr bullet, 2137 fps, delta fps/gr, 21.6

 

Preventing wobble is the best way to prevent out of balance. So I try to load all rounds more concentric and seat close to lands. A bullet that wobbles is slower down range than one that doesn't. Setting up a chroni  down close at target is best.

The 22 caliber Sierra 52gr. Match is probably the best bullet to experiment with JOE. It is more forgiving to excessive free bore such as the 223 NATO throat.

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Larry Gibson posted this 2 weeks ago

Joe

 

I'll email you.  Would be nice to see it here so all can see it though.

 

Here's another example of weight sorted 314299s at 100 yards from a CBA Military rifle match;

 

Shooting for score here so after a few shots in that raged hole at 12 o'clock in the 10 Ring I thought if I could just hold a tudge low I could move them into the X ring.........worked well for that 6 o'clock X but then the next shot dropped out the bottom for that 7 o'clock 10 (just cut the line!).....said heck with that and went back to aiming center and put the last 2 -3 into that ragged hole. 

Un weighed bullets just visually sorted will not do that. 

LMG 

Concealment is not cover.........

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joeb33050 posted this 2 weeks ago

Thanks for listing your chroni results.

WEIGHING BULLETS TO REDUCE VELOCITY VARIATION AND IMPROVE ACCURACY

 

 

 

223, 5.5 gr Titegroup, 40 gr bullet, 2063 fps, 53 gr bullet, 1784 fps, delta fps/gr, 21.5

 

 

 

223, 8.5 gr Titegroup, 40 gr bullet, 2678 fps, 53 gr bullet, 2374 fps, delta fps/gr, 23.4

 

 

 

22-250, 5.5 gr Titegroup, 40 gr bullet, 1857 fps, 53 gr bullet, 1622 fps, delta fps/gr, 18.1

 

 

 

22-250, 8.5 gr Titegroup, 40 gr bullet, 2418 fps, 53 gr bullet, 2137 fps, delta fps/gr, 21.6

 

Preventing wobble is the best way to prevent out of balance. So I try to load all rounds more concentric and seat close to lands. A bullet that wobbles is slower down range than one that doesn't. Setting up a chroni  down close at target is best.

The 22 caliber Sierra 52gr. Match is probably the best bullet to experiment with JOE. It is more forgiving to excessive free bore such as the 223 NATO throat.

 

I USE THE mAGNETOSPEED cHRONOGRAPH, ATTACHED TO THE BARREL.

I started with a variety of bullets, settled on Nosler 40 and 53 gr Varmageddon, for no particular reason-the 53 has an unusually high BC. I want a LOT of data, so need just a few bullet varieties.

See the post to come on titegroup  charge vs. mv linearity.

joe b.

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Starmetal posted this 2 weeks ago

If a bullet is out of balance you're not going to fix it.  Wobble and out of balance are two different things although related.  It is possible to have a near as perfect bullet that is balanced and then start it crooked. If so then it's not going to be accurate. 

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Larry Gibson posted this 2 weeks ago

Larry, I'd be happy to send you, or anyone, all the data. Just ask.

joeb33050@yahoo.com

 

Joe

Thank you for sending me the data.  As I mentioned before, you are to be commended for the compilation and correlation of  all that data.  There certainly was a lot of data!

 

In your summation you state; "Since I have not been able to find why .22 caliber cast bullets didn’t shoot accurately; I thought I’d find out if jacketed bullets with cast bullet powder charges would shoot accurately, and why."

I am not being critical joe, just trying to help you out.  There are three phases to ballistics; the 1st phase being internal ballistics.....that which happens in the barrel.  You certainly have compiled a lot of data concerning that phase given the amount of chronographed data.  The other phase you cover very well with a considerable amount of data is the 3rd phase which is terminal ballistics.  You have that very well covered with a lot of correlated group sizes. 

What is missing and why you can't find the answer from all that data to your basic question of; "Since I have not been able to find why .22 caliber cast bullets didn’t shoot accurately" is because you have not addressed the 2nd phase of ballistics.....external ballistics or the flight of the bullet and what happens during that flight.  It is within that 2nd phase of ballistics the answer lays.

Take those 55 gr Armcour FMJBTs for example.  You can measure them every way from Sunday, you can load them to very low ES and SDs yet they will still not be "accurate".  Why Because there is imbalances in the bullets probably caused by jacket thickness that is not uniform throughout each bullet and from bullet to bullet.  They are made to atypical military accuracy standards.  The Sierra's, Nosler's, Hornady's and other commercial made bullets are held to a much higher standard of manufacture.  It is the greater imbalances probably caused by uneven jacket thickness in the Armcour bullets that are adversely affected by the rpm during the bullets flight (external ballistic phase) that is the cause of the inaccuracy.  There is a very good chapter in the later Hornady reloading manuals that explains this.

So why can't we shoot cast bullets as consistently well as we do quality jacketed bullets?  The answer is because we can't consistently cast bullets as balanced as quality jacketed bullets are balanced.  Additionally cast bullets undergo a lot more deformation during the internal ballistic phase than do jacketed bullets.  All that means the jacketed bullet exits the muzzle better balanced than out cast bullets.  Given that the better balanced jacketed bullet will be less affected during flight by the RPM and thus more accurate.

By weight sorting our cast bullets we are attempting to find the most uniform cast bullets we have.  Those will also be the best balanced cast bullets we have to begin with.  With the best balanced cast bullets we have a better chance, if we load them correctly, of negating as much of the adverse affect the RPM will have on the bullets.  Thus the more accurate on target they will be.

LMG

 

 

 

 

 

Concealment is not cover.........

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joeb33050 posted this 2 weeks ago

 

"So why can't we shoot cast bullets as consistently well as we do quality jacketed bullets?  The answer is because we can't consistently cast bullets as balanced as quality jacketed bullets are balanced.  Additionally cast bullets undergo a lot more deformation during the internal ballistic phase than do jacketed bullets.  All that means the jacketed bullet exits the muzzle better balanced than out cast bullets.  Given that the better balanced jacketed bullet will be less affected during flight by the RPM and thus more accurate.

By weight sorting our cast bullets we are attempting to find the most uniform cast bullets we have.  Those will also be the best balanced cast bullets we have to begin with.  With the best balanced cast bullets we have a better chance, if we load them correctly, of negating as much of the adverse affect the RPM will have on the bullets.  Thus the more accurate on target they will be."

LMG

Larry;

How about some data showing that your opinions expressed above may be true?

Same weight bullets vs. varied weight bullets. If there's a 10% difference in 5-shot group size, to be 95% sure of that difference, one would need to fire 55 groups with each, measure and calculate.

Go to it!

joe b.

 

 

 

 

 

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Larry Gibson posted this 2 weeks ago

Joe b.

How about, before constantly requesting more data, you check out more closely what data has already been posted as in the chart/graph in a previous post.  There are 8 ten shot groups all of different weight bullets represented by their group size at 300 yards.  That is a representation of "same weight bullets vs. varied weight bullets".   The graph apply demonstrates the lighter weight bullets are less accurate.  It also demonstrates my contention that it is the top +/- .5 - .7 gr in weight variation that will prove to be the most accurate. 

The usual explanation of "weight sorting" is to segregate the bullets, by weight, into groups of .1 gr and then shoot those by group.  I have found that not to give more accurate results because the lighter weight ones still have enough imbalance in the bullet to cause inaccuracy.  While I do separate by .1 gr weight I do not then shoot by " each weight group".  I shoot the top end weight groups which will have (given a 158 to 185 gr as cast bullet) .5 - .6 gr variation or +/- .25 to .3 gr variation.  Those selected weight sorted cast bullets always give the best accuracy over the lessor weight bullets.  The reason is the heavier the bullet using the same alloy out of the same mould the better and more complete the fill out is and the less imbalance the bullet has. The axial center of bullet form will be closer to the axial center of mass which makes for a more accurate bullet.  

I haven't used 5 shot groups for many years, even multiple 5 shot groups.  The standard, even in CBA matches, is 10 shots whether for group or score.  Granted CBA commercial matches also shoot 5 shot groups in a match but 10 shot groups are also shot.  Since the 10 shot group is harder and a higher level of assurance of accuracy I use that hardest measure to get a higher assurance.....a ten shot group does give a higher assurance of accuracy than does a 5 shot group.  Might be why the 10 shot group is industry standard for test of velocity and pressure because it gives a higher "assurance".  

I have been shooting groups with weight and non weight sorted bullets for a long time now, both in matches and out of matches.  The results are always the same. Those selected weight sorted bullets always produce the best and most consistent accuracy.  I have produced and posted data supporting my contention several times now.  Should you care to disprove my contention then please do so, perhaps by conducting your own suggested test to get data you think is correct?  to ask me to do the same thing I have done over and over again using groups with less accuracy assurance when the results will be the same is, well, the definition of insanity.

Your conclusion that weight sorting does not improve accuracy based on your analysis of just the internal ballistics is still incorrect.  Again, not criticizing, just trying to help you understand. 

LMG

 

Concealment is not cover.........

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joeb33050 posted this 2 weeks ago

Data, Larry! 8 groups at different weight bullets neither demonstrates nor proves anything! Nothing! 10 shot groups? Go

to it! 5 shot groups inferior? Tell the N(send us some money)RA! The CBA NM includes both 5 and 10 shot groups. 

Get a gun, weigh some bullets, get out there and gather some data! All you've written is about opinion, give us some data! Data, that's what I sent you. Study it, learn what data is, and FIND SOME! I can and will help with your planning.

I am criticizing, just trying to help you understand.

joe b., the DATA guy

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Larry Gibson posted this 6 days ago

Not hardly.......

Nice to see you too, Frank.......

LMG

Concealment is not cover.........

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John Alexander posted this 4 days ago

Larry,

I agree that the theory you recite sounds reasonable.  No doubt significant imbalance in bullets degrades accuracy. Vaughn even tells us how much the deflection will be if we know how much imbalance (which we never do in actual practice.) To be useful any theory has to involve assumptions and those assumptions must be true. One bad assumption usually blows up the theory.

 For your theory, that lighter bullets in a batch are less accurate than the heavier ones we must assume: 1. that light bullets are caused by voids, 2. that those voids are not too near the longitudinal axis and, 3. that they are large enough to be significant.

 Unfortunately, we don’t know if any of these three are true much less that all three are true which is required for the theory to work. We seldom if ever find the dreaded voids so maybe light weight doesn’t indicate voids. (What does heavier than average bullets indicate?) The most likely location for shrinkage voids is near the long axis which would nullify their effect.  Voids of a few tenths of a grain are very small, is that enough to have a significant effect on accuracy?

 It is very hard to verify that these three assumptions are true so we are left, as we are with any theory, no matter how elegant, logical, or how much it seems it “just common sense” -- we have to test it. In this case show that light bullets are not as accurate as carefully weigh sorted bullets that don’t include light bullets.

 This isn’t hard to do and doesn’t require any equipment that a serious cast bullet shooter doesn’t already have. I suggest that any shooter who wants to know the truth do the following test.

 Cast a good quality batch of bullets of a proven design and hardness and sort for visual defects.  Weigh sort 50 bullets into 5 groups of 10 or 10 groups of 5 of sorted bullets.  Use the light bullets discovered in this process along with unsorted bullets to make an equal number of loads with at least one or two light bullets in each group. Load all the bullets identically using a proven load.

 The two types of loads (sorted and unsorted) should all be shot in one shooting session shooting the two types of bullets alternatively to avoid changing atmospheric, bore, or shooter conditions biasing the results.  Average the group sizes of each type of bullet and compare.

 I have done this with literally dozens of pairs of groups shot alternatively.  I have never been able to find a significant difference in the average accuracy of the sorted and unsorted (which contain the light bullets.)  The theory seems to be bogus for well-cast bullets perhaps because the small range of weights of well-cast bullets isn’t enough to affect accuracy.

 I stopped weight sorting bullets a long time ago and have fired lots of targets on good days equal to or smaller than the ones you posted.  Your statement that “Un weighed bullets just visually sorted will not do that” is not true because I and others have shot a lot of them.

 John

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frnkeore posted this 4 days ago

John,

What you say, has merit but, that type test, has to be done blind, in order to be accurate.

You've done your testing and it has proven to your standard.

I'm sure if LG did a test, it would come out with his testing proving he's right, too.

Only a fairly large sample, say 500 bullets, done blind, would prove anything.

Personally, I like as never perfect bullets as I can cast but, I've had "foulers" go into the same group, as my perfect bullets and shot groups to warm and foul the barrel,with those same foulers, that where also good groups. I've also had some of those "foulers" go other places!

Frank

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John Alexander posted this 4 days ago

Frank,

I agree that my experiments with sorted and unsorted bullets should have been done blind and they weren't.  I can't remember why I didn't. It could have easily been done.  I hope to repeat the tests and the next one will be done blind.

I don't agree that only a blind experiment can prove anything. Unless you mean "prove" tin the absolute sense, which can't be achieved anyway.  Some types of non blind experiment  can come close unless the experimenter is trying for the "right result"(being dishonest).  If you are going to be dishonest what's the point of the experiment -- just do it all at the keyboard which is not unheard of.

I don't know where you pulled "500 bullets to prove anything" out of but ten five shot groups will produce a pretty solid average that an additional twenty groups won't change much.

Your anecdote mentions that some foulers "go other places".  Before I stopped weigh sorting I sometimes noticed that some of my carefully sorted bullets also went other places and I'll bet yours sometimes do to.

You are not unique. We all like to have bullets as perfect as we can cast. The question is does weight sorting make them any more perfect in the sense that it shrinks groups. Or is it like sizing, lubing, loading, and shooting in the same order as cast (that some magic thinkers still believe makes more bullets more perfect) a total waste of time?

I am always amazed when a serious CB shooter admits that although he "believes" something like weight sorting helps.  Has never been curious enough to find out if it makes any difference when the test to find out with his own casting technique, bullet weight, and level of equipment and skill is easy to do.

John

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Ken Campbell Iowa posted this 4 days ago

...it occurs to me that the path to ultimate cast accuracy is more of a maze than a funnel ....  many improvements just lead to a blind end ... seemingly brilliant improvements are not necessarily additive ...

some amazing tweak  that cuts a 6 inch group down to three inches may also stop the group from getting smaller than 3 inches ..... and so the " literature " is full of ways to improve bad groups .... but not so much ways to make cast lead shoot as well as match jacketed bullets ...

the good news is that although we can't always get what we want ... with the knowledge dispensed by this CBA ... we might get what we need ...  1.5 moa fills a lot of needs ...

**************

just some midnight rambling .. apologies to the Stones 

ken

 

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joeb33050 posted this 4 days ago

We've fiddled around with this cast bullet shooting, seriously, for 30 years or more, and nothing has changed. My approach is to shoot a lot of jacketed bullets, then start making changes to try to get groups to increase to the cast bullet size. That will/may start to explain cast bullet inaccuracy.

Jacketed bullets

Drill a hole in the outer edge of 10 bullets, shoot 10 5-shot groups; 4 undrilled, 1 drilled, measure the groups.

Drill a hole in the base of 10 bullets, shoot 10 5-shot groups; 4 undrilled, 1 drilled, measure the groups.

Sound familiar?  The bullet's flight?

Who will drill these bullets for me?

joe b.

 

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RicinYakima posted this 4 days ago

Not a problem Joe, send them to me with instructions of where you want the holes, as I do that on my mini mill. Ric

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joeb33050 posted this 4 days ago

Not a problem Joe, send them to me with instructions of where you want the holes, as I do that on my mini mill. Ric

Thanks, Ric;

I sent you the ARMSCOR bullets and some Nosler 40 gr. I'll send more Nosler.

joe b.

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Starmetal posted this 4 days ago

Drilling holes in the side of the bullet unbalances them and if they are placed randomly in the chamber they will shoot a large group. Then if they are oriented in the chamber they will shoot a much better group. 

If someone is casting and gets more then .3 weight difference they aren't casting good.  As far as shooting lighter bullets and heavier bullets I've found if you shoot them in groups they group equally as well.  How does one know if the heavier bullets he casted aren't heavier because he didn't hold the blocks of the mold together the same each time? Or the stream of alloy was closer or not. They are many things that will change the weight of a bullet when casting. 

Franklore I like how you said we all done tests that met our own standard and testing.  You can even shoot lead paper patched bullets to high velocity in a fast twist barrel with very good accuracy. This fact alone proves it's not an rpm range making a cast bullet shoot inaccurately, but rather what the fast rifling twists does to the cast bullet while it is in the bore. 

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Larry Gibson posted this 4 days ago

All ballisticians know and understand the adverse affect an imbalance in a bullet, cast or jacketed, has on the bullet during flight.  To provide an example let's look at what Mr. Lilja has to say.  Please pay particular attention the bold highlighted 2nd paragraph.  Mr. Lilja understands it, all other ballisticians understand it, many shooters understand it, I understand but some do not  What is high lighted is a matter of ballistic fact.

 A Look at Bullet Imbalance and Twist

 By Daniel Lilja

Bullet imbalance--or more correctly, static imbalance--occurs when the axial center of gravity and center of form of a bullet are not concentric. It is easy to visualize the effect of this imbalance. As a bullet travels through a rifle barrel, it is being rotated about its center of form. When it exits the muzzle of the barrel, the center of rotation shifts from the bullet's center of form to its center of gravity. In mechanics the difference between these two centers is known as the radius of gyration. The bullet will travel in a roughly helical course, a corkscrew type path. Naturally the greater the divergence of the two centers, the greater will be the dispersion of the bullet from the point of aim.

As a bullet leaves the muzzle and is free to rotate about its center of gravity, if imbalanced it will diverge from the axis of the barrel at an angle that is dependant on the twist rate of the rifle barrel. The deviation angle = arctan (2e*Pi/T) where: e is the radius of gyration and T is the twist rate.

In the November, 1965 issue of THE AMERICAN RIFLEMAN, author E.H. Harrison describes the effects of this imbalance and its relation to rifling twist rate. In his article he derives a formula that calculates the amount of imbalance that will cause one minute of angle (MOA) target dispersion for a given twist rate. The formula is E=.000046(T), where T is the rifling twist rate and E is the amount of imbalance to cause one MOA divergence.

A computer program in Basic was written using the above formula to calculate the effects of a change in twist rate or the amount of bullet imbalance. The figures in the table are from this program. As can be seen from the table, the faster the rate of twist, the greater is the target dispersion. In this example, the amount of bullet imbalance is .0001". The twist rates are from one turn in 8 inches to one turn in 16 inches in one half-inch increments. These rates will cover 95% of the commonly used twists. The values under the heading "Expected `MOA' Accuracy" are just that. With a bullet with only .0001" imbalance, the best grouping at 100 yards that could be expected are these figures in inches for that given twist rate.

These `MOA' values are directly related to both the twist rate and the amount of imbalance. If either is doubled, the amount of target dispersion will also be doubled. From the chart it can be seen that an eight twist barrel will cause twice the amount of dispersion (.272 MOA) as a 16 twist barrel (.136 MOA). Likewise, if the amount of bullet imbalance were doubled, all the values under the `MOA' column would also be doubled.

It is obvious from this chart that two aspects of shooting are quite important. Namely, that we use high quality bullets and the slowest twist that will adequately stabilize that bullet.

It is easy to specify what twist barrel we want to use. It is more difficult, however, to determine the amount of imbalance our favorite bullet has. An obvious cause that comes to mind, in lead core bullets, is bullet jackets that have runout in the wall. It is not quite that simple, though. Let's take the example of a jacket that has .0003" runout, not uncommon in many jackets meant for benchrest shooting. That amount of runout does not translate into .0003" of bullet imbalance.

If the densities of lead and jacket material were the same, the amount of jacket runout would have little or no bearing on balance. They are not the same, though. The Machinery's Handbook, 22nd edition, lists the specific gravity of copper as 8.89 and that of pure lead as 11.34. Lead, then, is about 28% denser than copper. It follows then, that with a jacket with .0003" runout, the area of the jacket wall, on the thin side, that should have been occupied by jacket material has been increased in density by 28%. This will cause a shift in the bullet center of gravity away from the center of form by .28 x .0003" or .000084" (eighty-four millionths).

The above value is the approximate radius of gyration. This is an over-simplification but is probably a close approximation of the amount of imbalance. There are formulas in mechanics that allow for the calculation of the true amount of imbalance but they would require exacting measurements of each jacket and bullet shape. Obviously, greater amounts of jacket runout would cause a greater shift in the two centers.

It was mentioned above that if the densities of jacket material and lead were the same that it would matter little on the balance of the bullet. This is true as far as it goes, but it is known that when the ogive is formed on a bullet, if the jacket is not uniform, the nose of the bullet will yield to the thinner side causing to some extent static imbalance and irregular geometry.

There are other possible causes for bullet imbalance. When a bullet is fired from the cartridge case, it is under a great deal of pressure. Assuming that the barrel groove diameter is no larger than about .0005" over bullet diameter, the bullet will obturate in the barrel, conforming now to the diameter and geometry of the barrel. In the case of an oversized barrel, the obturation is probably not the full length of the bearing surface of the bullet. With a barrel that is the same size as bullet diameter--or undersized--the obturation will be complete and more of the bullet will assume the geometry of the barrel.

All is fine with this situation as long as the barrel is uniform. If the geometry of the barrel is such that the groove depths are not the same, the bullet has now gained static bullet imbalance from the barrel that it did not previously have. There are other possible causes for static imbalance. The lead core may have a flaw, such as a void or air trapped between the jacket and core during core seating. The results are the same.

Another cause of imbalance is a barrel chamber that is not in alignment with the axis of the barrel. The effect is that the bullet enters the rifling misaligned, cocked in relation to the rifling. Again the bullet has gained imbalance from the barrel. In his article, Harrison lists this cause as "yaw" in the barrel.

Besides the above-mentioned cause for imbalance from jacket wall runout, the bullet can obtain imbalance from a swage die that is not geometrically perfect. The bullet may come out of the die less than round, or with an ogive that is not in line with the rest of the bullet. Harrison lists this type of cause as "dynamic imbalance". It also can cause static imbalance.

 

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John Alexander posted this 4 days ago

Starmetal says,

 "Drilling holes in the side of the bullet unbalances them and if they are placed randomly in the chamber they will shoot a large group. Then if they are oriented in the chamber they will shoot a much better group."

 Yes, and I have oriented them in positions around the clock and shot a big group in the shape of a donut with no hits in the middle -- If the drilled holes are big enough.  Mann pretty much nailed deflections caused by imbalance 110 years ago.

 I agree that well- cast bullets don't vary much in weight.

 "As far as shooting lighter bullets and heavier bullets I've found if you shoot them in groups they group equally as well. "

 It's more than sorted light bullets will shoot well.  In the pairs of groups I shot, the "bad bullets" were always unsorted or were mixed light and heavy bullets to make a more extreme range of weights but the “bad” bullets always gave the same result -- no difference in average group size from the sorted bullets.

John

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Larry Gibson posted this 4 days ago

John

"For your theory, that lighter bullets in a batch are less accurate than the heavier ones we must assume: 1. that light bullets are caused by voids, 2. that those voids are not too near the longitudinal axis and, 3. that they are large enough to be significant."

Ergo is the problem in this discussion.  I do not subscribe to any of those 3 assumptions.  In fact if you re-read my post with the graph I explain what I've found to be the real problem and it is not the suspected or assumed "voids" in the bullets.  Yes, that's what we've all been told for probably a hundred years and it is what we've based our testing on. 

Ten years ago I thought I was casting pretty good bullets, excellent in fact.  However. the more I got into shooting cast bullets at HV I found while I was casting good, excellent bullets I too hit the accuracy wall that joeb is alluding to.  I also found that when those cast bullets were pushed to really HV (2500 - 3000+ fps) they did not do as well as expected.  Back then I was weight sorting as we've all been told to.  If you line them out by weight you get the so called "bell curve".  In proving insanity I, like you and everyone else, then did the same testing of each .1 gr testing over and over again expecting different results.....we all got the same results; accuracy was not really improved via that method no matter how many times we ran the test.  You are asking me now to run the same test and think I will come up with different results?  It wouldn't happen.

Let's assume we have a mould that will cast perfectly even bullets in all dimensions.  Not an assumption but fact is that mould has a finite capacity for any alloy.  Thus if we cast with a good alloy giving the best fillout then only those that weigh the heaviest will have filled the mould out completely.  Any bullets with less weight are then not dimensionally the same.  We may not be able to measure other than weighing that difference but the difference is there in lighter weight bullets none the less.  Now that difference in weight (mass) is there but it is not predictable.....we don't know where in or on the bullet that difference in weight is missing from.  The missing weight is what creates the imbalance.  I suspect voids in the alloy are not the problem but rather other aspects are which I have previously discussed. 

Going back to the previous post with the graph; on that graph are 8 ten shot groups (or 16 five shot groups if you want) of the top end of weight sorted bullets.  Those groups were shot at 300 yards with 2900+ fps velocity.  It shows that the lighter weight bullets were not as accurate as the heavier bullets.  Those heaviest bullet gave consistent moa accuracy at 300 yards.  There was no "bell curve" to that weight sorted batch of bullets as mentioned in the previous posts. 

 

I recently cast 542 NOE 30 XCB bullets of #2 alloy.  I have just completed weight sorting them.  In the next post I will show the graphed results of the weight sort which should aptly demonstrate what I'm saying.  Have to copy, download, etc. so it will be an hour or so.

 

LMG

 

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Starmetal posted this 4 days ago

That difference in weight between bullets can very well be in the sprue itself. Each sprue cut is different especially if the amount of freeze time before cutting varies.  Thus if the weight difference is indeed in the sprue then the diminsions of the bullet are the same between different weights. 

 

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Starmetal posted this 4 days ago

45 2.1 is a very good caster.  I'd call it professional. I visited with him a few years ago and we took his Ruger Scout in 308W out to shoot. I sat there and watched him load the ammo.  LC cases and used the 30 silhouette bullet. He sized the cases normally and just picked the bullet out of a can of bullets. He doesn't weigh sort his bullets. No need for him as the vary minutely between one another. He loaded these over a duplex load of surplus 867 with a 4198 booster.  He shot at 100 yards and shot a tight 5/8 inch group. Then I shot his rifle and shot just a sligthly larger group and I mean minutely larger.  The rifle repeatedly shot the same groups over and over with no flliers. BTW that was at between 2300 to 2400 fps. Alloy was water dropped 50-50. 

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Larry Gibson posted this 3 days ago

Here is the results of the weight sort.  542 bullets were cast of Lyman #2 alloy and WQ'd.  They were then aged about 12 days before I got around to weight sorting.  Here is my set up for weight sorting.  I visually inspect each bullet for any defect.  If any is found that bullet is rejected to be melted and recast at a later casting session.  Those that pass my anal visual inspection then have any remnant of the sprue cut off.  That is done on the lead block with a sharp blade on the pocket knife.  The bullet is then weighed on the Redding balance beam scale.  While waiting for the beam to settle I then visually examine and sprue cut another bullet.  With the magnifier in front of the scale I can readily and accurately see what the weighed bullets exact weight is. The bullet is then placed in a bin for that weight. 

Of the 542 bullets weighed 22 were rejected for a visual defect or because they weighed less than 186.9 gr which means the weighed ones had passed the visual inspection but still weighed way lite.  The remaining 520 XCBs were weight sorted into separate bins of .1 gr increment from 186.9 gr to 188.0 gr......a 1.1 gr spread.

 

Here is the rough graph of the weight sort.  As you can see there is no "bell curve".  The curve rises from 186.9 gr slowly to 187.5 gr and then rises sharply.  The "curve" then plateaus out at 187.7, 187.8 and 187.9 gr with 113, 124 and 110 bullets for each weight.  The "curve" then falls sharply to just 9 bullets at 188.0 gr.  Of those 9 bullets only 2 actually weighed 188.0 gr. The remaining 7 bullets weighed between 187.9 and 188.0 gr.  There were no bullets heavier than 188.0 gr. 

What the weight sorting is showing us is the 113 bullets of 187.7 gr, the 124 bullets of 187.8 gr and the 119 bullets (I'll put the 188.0 gr bullets in with those) of 189.9 gr weight had the highest weight/mass of alloy in them.  Since the curve dropped off suddenly we see those weight bullets are the most consistent and the best the mould will produce with that alloy.  Those 356 weight selected bullets will be used for best accuracy. 

The 187.6 gr bullets will be used as fouler/sighters as I expect they will give very good accuracy also given only a .2 gr +/- difference in weight.

Had we lumped all the visually selected bullets into one group 70% would have been with the excellent bullets, Another 15% would have been with the fouler/sighter bullets and the remaining 15% would have been with bullets having a weight/mass difference of 1.1 gr.  Now, had I done that I probably would have got nice 1 1/2 moa groups with 7 +/- shots going into moa or less and 2 -3 +/- shots going out of the group in the 1 1/2 moa +/-.  How many of you shoot groups like that with bullets only visually sorted?   

It is with such weight sorted selected bullets (the 187.7 to 187.9 gr bullets) that I am able to hold moa accuracy to 300 yards and beyond with a 2900+ fps velocity. 

That is how I weight sort and why it makes a difference.

 

LMG

 

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Starmetal posted this 3 days ago

 When I shoot for accuracy I weigh my bullets. I don't have much a weigh variance between my bullets.  I still will sort them into alike weights.  I have found no difference is accuracy between the weights as long as you are shooting the same weight bullets in your groups may them be 5-10-or 20 shot groups.  My conclusion is that to get the best accuracy you must weigh your bullets. If your weight variance isn't much between bullets it won't make a lot of difference. Weighing does sort out a bullet that is way different even though visually it shows no defects so in this sense weighing is a good thing.  It also can be done extremely fast on a digital scale. It will drive you crazy to try to use a balance beanm scale.  For the real anal it may be a good ideal to weigh your gaschecks. 

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frnkeore posted this 3 days ago

Frank,

I agree that my experiments with sorted and unsorted bullets should have been done blind and they weren't.  I can't remember why I didn't. It could have easily been done.  I hope to repeat the tests and the next one will be done blind.

I don't agree that only a blind experiment can prove anything. Unless you mean "prove" tin the absolute sense, which can't be achieved anyway.  Some types of non blind experiment  can come close unless the experimenter is trying for the "right result"(being dishonest).  If you are going to be dishonest what's the point of the experiment -- just do it all at the keyboard which is not unheard of.

John, it's not about being dishonest. If you'll look up why blind testing is done, you'll find that results can be subconsciously skewed, when you think you know the out come. That's one of my issues with LG's testing. If you want me to believe in any testing, it has to be done blind and that would include, someone else, other than the person intimately involved in the out come, doing the shooting. 

I don't know where you pulled "500 bullets to prove anything" out of but ten five shot groups will produce a pretty solid average that an additional twenty groups won't change much.

500 was a number (50, 10 shot groups) that, in my option, would be conclusive and no one could say that, it wasn't enough. I think Joe B would agree? 

Your anecdote mentions that some foulers "go other places".  Before I stopped weigh sorting I sometimes noticed that some of my carefully sorted bullets also went other places and I'll bet yours sometimes do to.

Yes, but, I still don't shoot imperfect bullets.

When I've tried to help some of the newer match shooters, that are having trouble grouping, I always look at their bullets first and I've found that most of the time, the bullets don't look to good. Usually they have rounded, uneven bases, with flaws here and there in the grooves. I have asked that they let me barrow their mold and cast a batch and in every case, they did better with the bullets that I cast for them. Some times they are using "junk" lead, of unknown hardness too, that in breech seating, can make a big difference.

You are not unique. We all like to have bullets as perfect as we can cast. The question is does weight sorting make them any more perfect in the sense that it shrinks groups. Or is it like sizing, lubing, loading, and shooting in the same order as cast (that some magic thinkers still believe makes more bullets more perfect) a total waste of time?

I am always amazed when a serious CB shooter admits that although he "believes" something like weight sorting helps.  Has never been curious enough to find out if it makes any difference when the test to find out with his own casting technique, bullet weight, and level of equipment and skill is easy to do.

John

I don't always weight sort but, I usually do, for my big shoot, in Spokane, each year. I'm not sold that it helps but, it does make me feel more confident and if I do it, I have the time to. Spending time to feel better and be more confident about your shooting, isn't a bad thing, is it?

Frank

 

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Starmetal posted this 3 days ago

Bullets weighing the same have to make a difference.  The question is how much variance between them has no effect.  If weight wasn't that important then why do bullet manufacturers strive to make all their jacketed bullets weigh the same? 

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Larry Gibson posted this 3 days ago

Frank

Regarding the testing I do, I report and learn from the test results whether the results agree or disagree with any pre-conceived contention I may have.  One of the biggest complaint is I now say something's a bit differently than I said 12 +/- years ago.  Well, 12 +/- years ago when I began seriously theorizing about the RPM Threshold I was only making educated guesses.  I put my money where my mouth is and conducted a lot of different tests involving thousands of rounds out of numerous different rifles and cartridges.  That testing demonstrated I was correct about many things but wrong on others.  The test results over the last 12 + years has caused my mind to change on some things and has caused the RPM Threshold concept to change and evolve into what it is today. That is what objective scientific testing does for us; validates or invalidates our assumptions. 

Most scientific testing is not conducted "blind".  I have over 2600 HV rounds (2500 to 3100 fps) out of my 30x60 and over 2000 rounds through my 10, 12 and 14" twist .308W rifles in conducting tests on this topic.......many of which are duplicate and quadruplet tests requested by many, including you.  I've also been shooting CBA matches for the last 3 years because you requested......and I win because I objectively use the results from my testing.

Nice to see both you agree with me on weighing cast bullets and the need to cast quality bullets to begin with.

 LMG

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Larry Gibson posted this 3 days ago

We've fiddled around with this cast bullet shooting, seriously, for 30 years or more, and nothing has changed. My approach is to shoot a lot of jacketed bullets, then start making changes to try to get groups to increase to the cast bullet size. That will/may start to explain cast bullet inaccuracy.

Jacketed bullets

Drill a hole in the outer edge of 10 bullets, shoot 10 5-shot groups; 4 undrilled, 1 drilled, measure the groups.

Drill a hole in the base of 10 bullets, shoot 10 5-shot groups; 4 undrilled, 1 drilled, measure the groups.

Sound familiar?  The bullet's flight?

Who will drill these bullets for me?

joe b.

 

Joe b.

I have conducted that very test numerous times.  The last was with loaded 7.62 NATO M118SB.  I drilled a whole in the side of the bullet just in front of the case mouth.  The hole was just deep enough to just go through the jacket.  I then shot 10 shots out of a 10" twist .308W rifle of undrilled M118SB and then 10 shots out of the same rifle with the drilled bullets.  Range was 100 yards. The velocity averaged 2666 fps at 63K psi.  Here are the two groups with the left being the undrilled M118SB right out of the box.

 

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Starmetal posted this 3 days ago

I've found in my life time of shooting cast that if you have a good cast bullet, that if it fits the throat, that if you get that bullet started straight into the bore, and that you use the right alloy for the pressure range that you are shooting that fast twist rifling doesn't make an iota of difference in accuracy at high velocity. I've proven this with shooting various calibers with various fast twists.  Today it's more common now to see cartridges such as the 22-250 shoot just as accurate with very fast twist for that caliber and they shoot all weight bullets equally accurate. Talking to some very notalble and respected ballisticians I was told they wouldn't tell me what fast twist rate it would take to start to affect the accurazy of a bullet from over spinning it because nobody would believe it. If you read a lot of books one shooter stands out in trying all the rifling twists he could and that person was Pope.  It blew my mind that he even tried a 1 in 1 twist. I believe Mann done the same thing.  When I first got my Colt HBAR AR 15 with a 7 twist I looked down the bore and said "Oh Lord"  It looked like threads after having dealth with  slower twists like 10-12- etc.  Well I found out the rifle shot very well. It didn't seem to make much difference what my bullet weight (thus length) was as long as the bullets were quality bullets and the load for them was good.  RPM only affected bad bullets and that can be ones started crooked to ones with major defects.  In reality the centrifigal force of the bullet spinning tries to stabilize the bullet through the gyroscopic action. This is seen when bullets "go to sleep" at a certain distance. Nothing, not even this  gyroscopic action can stabilize a bad bullet. 

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Starmetal posted this 3 days ago

Drilling a hole in a bullet and shooting a group with a bunch of them proves only that the rpm from the twist will act upon what is bascially an unbalanced bullet and it will be a negative action. Instead try a test where you removed the same  amount of weight as that drilled hole except in the very center of the base of the bullet.  Shoot those and see what the group is. 

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frnkeore posted this 3 days ago

Frank

Regarding the testing I do, I report and learn from the test results whether the results agree or disagree with any pre-conceived contention I may have.  One of the biggest complaint is I now say something's a bit differently than I said 12 +/- years ago.  Well, 12 +/- years ago when I began seriously theorizing about the RPM Threshold I was only making educated guesses.  I put my money where my mouth is and conducted a lot of different tests involving thousands of rounds out of numerous different rifles and cartridges.  That testing demonstrated I was correct about many things but wrong on others.  The test results over the last 12 + years has caused my mind to change on some things and has caused the RPM Threshold concept to change and evolve into what it is today. That is what objective scientific testing does for us; validates or invalidates our assumptions. 

Was that before or after I started posting the CBA match winning RPM, 3 or so years ago?

Most scientific testing is not conducted "blind". 

It's done blind, when they want the true answer. You can skew the results, even though you THINK you aren't doing that. Please read up on it.

I have over 2600 HV rounds (2500 to 3100 fps) out of my 30x60 and over 2000 rounds through my 10, 12 and 14" twist .308W rifles in conducting tests on this topic.......many of which are duplicate and quadruplet tests requested by many, including you. 

I asked that you test with the same action, using the same barrel maker and that the chambers be done by the same gunsmith, only the twist be different. You used 3 completely different rifles.

I've also been shooting CBA matches for the last 3 years because you requested......and I win because I objectively use the results from my testing.

While I have yet to see any posted match results on you (I've looked online in in the Fouling Shot), admittedly, if you've won anything, it's in the Milsurp, LV classes not, any target classes at HV.

I'm glad that I have the power to get you to shoot in CBA matches, even if they are only the Milsurp ones

Nice to see both you agree with me on weighing cast bullets and the need to cast quality bullets to begin with.

Yes, we agree on that

 LMG

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Larry Gibson posted this 3 days ago

Frank

Was that before or after I started posting the CBA match winning RPM, 3 or so years ago?

No, please read the paragraph you're responding to.  That was 12 +/- years ago....well before I knew you.  You posted 1 match winning RPM.  All the others were below the RPM Threshold. 

It's done blind, when they want the true answer. You can skew the results, even though you THINK you aren't doing that. Please read up on it.

No need to read up on it.  SAAMI testing is not done "blind", neither do the ballisticians who develop factory ammunition, ballistician/technicians who develop loads for reloading manuals nor the ordnance personnel who develop military loads test "blind".  They test objectively.  Because you disagree with the results does not mean the test was "skewed", not objective or not conducted correctly.  If you have results from your own test demonstrating anything to the contrary please feel free to post them?

I asked that you test with the same action, using the same barrel maker and that the chambers be done by the same gunsmith, only the twist be different. You used 3 completely different rifles.

What you asked would make not difference.  Please feel free to conduct the same test spending your own money on such.  Even then you will find the results emulate those my test produced.  The problem is you still don't understand the use of 3 different rifles of the same cartridge with different twist was a valid test because the accuracy of each rifle compared to the other 2 rifles was not the question.  The question was at what velocity/RPM each rifle began to lose accuracy.  In other words each rifle was only compared to itself.  Furthermore your suggestion isn't correct because the assumption of the same load being used to "compare accuracy".  Different loads (just the different powder charges actually) were used to achieve the velocity necessary.  The slower the twist the higher the velocity was required to reach the RPM level where accuracy began to be lost. 

While I have yet to see any posted match results on you (I've looked online in in the Fouling Shot), admittedly, if you've won anything, it's in the Milsurp, LV classes not, any target classes at HV.

For what ever reason The Phoenix group is at consternation with the CBA powers that be and aren't submitting match scores.  I've no idea why but if you PM me your email address I will send you some match results.  I also shoot commercial rifle with my .308W M70 target rifle.  The velocity of the load I used last was 2300+ fps.  Didn't win but I did ok.  I haven't had time to really develop a load for that rifle yet.  Why don't I shoot my HV 30x60 XCB?  It was built as a bench rest rifle and would only fit into "unlimited" class, does not fit into the "commercial rifle" class (mostly what the boys in Phoenix shoot) and since I try to stay within the rules I don't use it. 

I'm glad that I have the power to get you to shoot in CBA matches, even if they are only the Milsurp ones

Not sure you had "the power" but I do thank you, the guys in Phoenix are a great bunch and I enjoy the matches. They shoot the military matches alternating months with the commercial rifles.  Since it is a 3 1/2 hour drive one way I like to shoot the matches I enjoy not the ones you think I should.  BTW; I weight sort the 314299s used in the M39 MN.  For accuracy it matters not what the velocity is, what matters is a quality cast bullet.  That's why I weight sort; to use the best quality cast bullet I can and that's why I do quite well.

LMG 

Concealment is not cover.........

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frnkeore posted this 3 days ago

No, please read the paragraph you're responding to.  That was 12 +/- years ago....well before I knew you.  You posted 1 match winning RPM.  All the others were below the RPM Threshold.

I did read it and I know the subject well. You and I have had many discussions about it on the Boolit forum. I posted several CBA match scores, thorough the nation. At that time, you said that the threshold was 120K. Your threshold, is indicative of where accuracy should degrade yet, people where winning matches, above it. You stated that the CBA competitors may not be giving truthful info and you where RIGHT. I see now that you have raised it to 140K, apparently to cover the higher RPM, match winning competitors.

SAAMI testing is not done "blind", neither do the ballisticians who develop factory ammunition, ballistician/technicians who develop loads for reloading manuals nor the ordnance personnel who develop military loads test "blind".

SAAMI doesn't try to prove a theory, you are.

Why don't I shoot my HV 30x60 XCB?  It was built as a bench rest rifle and would only fit into "unlimited" class, does not fit into the "commercial rifle" class (mostly what the boys in Phoenix shoot) and since I try to stay within the rules I don't use it.

Really? You do it for their sake? UNR is hardy any different, accuracy wise than the Heavy class. Many heavy rifles produce better scores than UNR. As far as I know, CBA doesn't have a Commercial Class so, I guess you don't really shoot CBA or they would have to allow that rifle! Also, I believe that I read a forum post, where you said you would shoot it but, it wasn't competitive in the target classes.

Frank

 

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Larry Gibson posted this 3 days ago

Frank

The Phoenix boys call it commercial rifle matches.  That's what I shoot in because they mostly shoot "Production Rifle" and "Heavy Rifle" (CBA Rules 5.2 and 5.3) .  My 30x60 doesn't fit, by the rules, in either class so it would fall under "Unrestricted Rifle" (CBA Rule 5.4) by the rules .  As I said it wasn't designed as a bench rest rifle, particularly to compete in that class.  Besides, no one there shoots in that class so regardless I would win by default.....a lot of sense that would make. 

 You know you're free to post your own opinions on topics and results of actual tests you have done here......just as I am free to post my opinions and test results here.  I have posted a considerable amount of test results about weight sorting bullets.....can we discuss that instead of the personal criticism?

LMG

Concealment is not cover.........

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John Alexander posted this 3 days ago

Larry wrote:

"Ergo is the problem in this discussion.  I do not subscribe to any of those 3 assumptions.  In fact if you re-read my post with the graph I explain what I've found to be the real problem and it is not the suspected or assumed "voids" in the bullets.  Yes, that's what we've all been told for probably a hundred years and it is what we've based our testing on."

Larry,

You are right you didn't claim it was assumed voids causing the light bullets to shoot poorly.  You talk about unbalanced bullets so often I jumped to that conclusion. I apologize.

Your detailed description of how you sort bullets was somewhat interesting especially that you do it with a beam balance. You must have the patience of Job. In spite of the good description of your weighing, at the end of the post you simply told us that the light weight bullets were inferior. I expected you to present your test results proving the light weight bullets were inferior.  We already knew your opinion.  Since that opinion is counter to what I have found in large number of tests I was disappointed.  Shooting  some groups to support your opinion would have taken less time than all the weighing and trimming bases.   

Your earlier tests of groups at 300 yards gave a "hint" that the light bullets were inferior. The groups of light bullets were somewhat larger. But in ten shot groups even at 200 yards it is common for adjacent groups to vary by well over 50%. At 300 the variation would be greater. Two groups with the light bullets is just too few for drawing conclusions.

I plan to do some testing on light vs. heavy bullets in the spring.  Maybe my results will support your opinion but they never have in past tests.

Helpful hint -- If you cut sprues with a gloved hand while applying down pressure you won't have to trim bases because they will be visually perfect as they drop.

John

 

 

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Larry Gibson posted this 2 days ago

John

Yes, groups at longer range especially, can vary quite a bit group to group.  In the test I did there are 8 ten shot groups fired at 300 yards.  Five consecutive ten shot groups with the match select weight sorted bullets follow the 2 light bullet groups.  If that variation were going to appear it should have been evident after 80 shots in the 8 ten shot groups.  Fact is the only variation was the first 2 ten shot groups using the light weigh non-select bullets.  There is little practical variation between the 5 following ten shot groups.  I would venture that is more than a "hint".

You previously stated; "ten five shot groups will produce a pretty solid average that an additional twenty groups won't change much."  In the test I shot 8 ten shot groups (or 16 five shot groups if someone wants to look at five shot groups) for 80 shots......so how is it if 50 shots works then why isn't my test of 80 shots producing a "pretty solid average"? 

And yes, I will load the "inferior" bullets and test them.  There are only 83 "inferior" weight bullets total. Thus the problem is in 3 of the seven "inferior" weights there aren't enough for a single five shot group.  Only in two of the "inferior" weights is there enough bullets for multiple five shot groups or 2 and 3 ten shot groups.  I'll come up with something.

I normally use a gloved hand to cut the sprue on 1 and 2 cavity moulds.  That does make for a much cleaner cut as you mention.  However with 4 and 5 cavity NOE moulds I don't have enough leverage on the sprue plate to cut that many sprues, especially if a harder alloy like #2 or linotype is used.  Tried for a while but kept burning my hand through the thick glove and wasn't getting the sprue cut quick enough to get the bullets into the water for a proper HT.  Perhaps someone with more strength and larger hands than I have can use gloves on those moulds but I can't.  Thus I am stuck with trimming the sprue off.  It actually goes quick because while I am inspecting and trimming off the sprue on one bullet the scale will balance with the previous.  Not any waiting between bullets for the scale. 

LMG

 

 

 

Concealment is not cover.........

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OU812 posted this yesterday

The true sign of intelligence is not knowledge, but imagination. Albert Einstein

I'm going to work on my bump die.

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45 2.1 posted this yesterday

This was posted in this thread:

 A Look at Bullet Imbalance and Twist

 

 By Daniel Lilja

Bullet imbalance--or more correctly, static imbalance--occurs when the axial center of gravity and center of form of a bullet are not concentric.

The above sentence is the answer to the CBA's quest for better accuracy than what you see now. Note the sentence was from Daniel Lilja, maker of fine barrels. Note the word "static" which means at rest or not in motion. Basically he is saying your bullet is out of line with the bore. Your cartridge, the bullets holder, is holding it out of line with the centerline of the bore. Irregardless of what you do, without the bullet entering the bore straight, your quest for accuracy is half gone right there. This is the thing that produces large groups and fliers. There are simple ways of defeating this problem...... first you are shooting undersize, too hard of bullets and you have cases laying in the bottom of the chamber out of line with the bore. If you fix those two things, you don't need to be concerned with bullet imbalance as quoted by Lilja and others here. Fix those things and you will get unbelievable accuracy, even out of production rifles.

How do you fix that..... try the old Lee red/black box dies..... they work along with some other things.

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