Why weigh bullets?

  • 15K Views
  • Last Post 30 September 2010
CB posted this 21 June 2007

(this thing is getting too messy, I can't find things. I'm going to start new topics as needed.)

Why I weigh cast bullets.

 

A. Weighing allows me to eliminate “strangers". My average lot size over some 14620 cast bullets weighed and recorded is 107. This does not include the “strangers", those bullets that weigh more than a half a grain away from the mean. I generally find 1-3 of these. I assume that these strangers will shoot less accurately.

B. Weighing allows me to segregate or class bullets. I shoot sets of 25 shots, every set is an experiment. I need sets of 25 bullets plus 1-2 in case I drop one. After weighing it is easy to select these sets of bullets with little or no weight variation within each set.

C. Weighing allows me to understand better what is going on during casting. For example, I had suspected trouble with a lot of 25:1 that I bought, and had been casting with a mixture of lead and a little foundry type. After each lot I added lead to the pot, wanting softer bullets. Each lot had the average weight increase. This lot has an average of 183.6 grains, and a standard deviation of .171 grains.(183.3-184.0 only.) There's not enough ?tin?, certainly not enough something, because the quality of the bullets has gone down based on the variation and the appearance. There are many other lessons I've learned by weighing bullets.

D. Weighing allowed me to calculate and record the average weight and standard deviation of weight of each lot of bullets cast; and this data leads me to this conclusion: After eliminating “strangers", the standard deviation of bullet weights, on average, for >14000 bullets, is .151 grains-and this includes some very messy results. Then it is reasonable to say that under proper conditions a caster should be able to cast bullets that weigh +/-.5 grains virtually every time, and with culling, lots of bullets can be held to +/- .3 grains easily. ( I suspect that variation is not a function of average bullet weight, but don't know, yet.)

 

Does weighing cast bullets matter?

Based on the results of the testing performed with round-filed bullets in 2007, it appears that pretty big holes or bubbles in cast bullets have a pretty small effect on accuracy.

In the arena where average five shot group size at 100 yards is 2” or greater, weighing bullets may not matter.

Where average five shot group size at 100 yards is <2", it MAY be true that careful inspection, weighing, culling and segregation substantially reduce group size.

It has often been stated that with average group sizes well under 1", that weight variation within the feasible range increases group size substantially. However, data to support this belief is sorely lacking, and needed.

 

Why does cast bullet weight vary?

This is what I think, not what I know.

Bullet weights from the same pot of alloy vary, at least mine do, even after visual inspection and culling under a 4X lighted magnifier.

I think that there are only a few causes of this weight variation.

First is holes or bubbles in the bullet, not visible during inspection.

Second is “incomplete fill out” or rounding of some edges, slight enough to be missed during inspection.

Third is due to variation in weight due to variation in diameter/shape due to variation of the pressure with which the mold is held closed.

I think that weight variation due to alloy composition is ruled out because of the “same pot of alloy” condition.

joe brennan

Attached Files

Order By: Standard | Newest | Votes
PETE posted this 21 June 2007

 Joe,

Third is due to variation in weight due to variation in diameter/shape due to variation of the pressure with which the mold is held closed.  You can also add variaition in pot & mould temp. will affect bullet wgt. All the pots I've used over the years start out varying about 10 degrees from lite on to lite off. As they age this increases to about 20 degrees when it seem to stabilize. I don't know of anything you can do to correct this either.

  Then mould temp. has been shown to affect the wgt. I'm sure we've all noticed that bullets tend to get heavier toward the end of a run. Some tests have been run with thermo-couples attached to moulds and the mould allowed to vary in temp. and the wgt. of the bullets recorded. This mould temp. seems to be the critical factor in bullets varying in wgt. The closer you can keep the temp. the closer your wgt. variation will be.

  Added onto to your reasons it does seem a wonder that we can cast anything like close wgt. bullets. Sometimes some of my casting sessions would make you think I had all the above problems at the same time! :)

I think that weight variation due to alloy composition is ruled out because of the “same pot of alloy” condition.   I agree and it's why I keep all bullets from the same pot of alloy separate.

PETE

Attached Files

CB posted this 25 June 2007

Joe Brennan wrote: Does weighing cast bullets matter?

It has often been stated that with average group sizes well under 1", that weight variation within the feasible range increases group size substantially. However, data to support this belief is sorely lacking, and needed.   

Bottom line is what shows up on the target. My experience has shown me that segregating bullets from a two cavity mould helps, indexing bullets by placing a small mark on the ogive helps, using wind flags helps (big time). Weighing to +/- a tenth grain in a normal casting session doesn't seem to make much of a difference.

To me this is a lot like weighing vs dumping powder charges. Weighing hasn't been proven to improve accuracy while it seems that it should. If someone can prove that weighing made a substantial difference I'm all ears but up to this point what's been said and proven to the shooters that did the comparison is that it doesn't.

I don't think I have the casting skills to drop bullets with intentional voids or 1 1/2 grain weight variations so maybe weighing would help in those cases. I don't start saving bullets until the mould and pot are up to temp. and throw back bullets where the base isn't filled out so maybe that why I don't see any difference between “match grade bullets” and foulers.

Or maybe I just don't set the bar as high. 

Pat

 

Attached Files

PETE posted this 25 June 2007

 Pat,

Weighing to +/- a tenth grain in a normal casting session doesn't seem to make much of a difference.   I think you're probably right and a looser spread might work just as well. But I don't know how much that would be so it makes me happy to keep it as tight as I can! :)

  It would be an interesting test, if it was possible to do it, to see, say for a .30 cal., how much variation it actually takes to get a noticeable difference in accuracy. I don't know. So I weigh all my bullets.

  For your own use what would you consider to be an acceptable spread?

  The one thing I've found in casting over the years is that every session will have several bullets that will weigh .5 gr. + or-, or more, from the norm. Sometimes if the phase of the moon isn't quite right they'll be a full gr. off. They can even be heavy, which does tend to confuse me. The ones that go light I assume have a void in them.

  With the electronic scales we have these days I like to get rid of these “weird” bullets.

PETE

Attached Files

CB posted this 25 June 2007

Pete,

Most of my casting is with one cavity  moulds and if I use a two cavity the bullets are segregated. Once the mould and pot are up to temp and throwing good bullets weighing a batch will show 6 or 7 tenths difference on average with the majority within +/-  2 tenths of mean. I wouldn't know how to cast a batch of bullets with enough weight variation to be able to find out how much would be necessary to show on the target but I don't think a half grain does .  

We could discuss this stuff til we're blue in the face and I'll continue to weigh and segregate the bullets I shoot in matches into +/- 1 tenth groups but I don't think it's gaining me anything except peace of mind.

This seems like such an easy thing to test for oneself that further hypothetical discussion on it seems useless.  I don't think one person who's replied to the weighing bullets threads has said they were able to prove to themselves weighing showed up on the target.

Pat

Attached Files

CB posted this 25 June 2007

I agree with Pat. I use 2 cavity moulds for my match stuff and I do weigh them in 1 tenth groups, mainly for peace of mind and that is how I was taught.

Other than that I have no data that either supports or disproves that it makes a difference.

Attached Files

billwnr posted this 25 June 2007

I use a 4 cavity NEI and weigh and order my bullets. I use a bump die and that negates any differences between the 4 mould cavities.

Attached Files

PETE posted this 25 June 2007

 Pat,

We could discuss this stuff til we're blue in the face and I'll continue to weigh and segregate the bullets I shoot in matches into +/- 1 tenth groups but I don't think it's gaining me anything except peace of mind.   Exactly! After you've worked up a good load it becomes more a matter of confidence in yourself that counts the most. To me, at least, this is eliminating all the variables I can think of so that little gremlin doesn't sneak into my mind questioning whether that bad shot was one of those things I didn't take care of.

  Here's one for you to think about. :) I got to thinking one time if maybe a guy ought to face in a certain direction in relation to the range he'll be shooting on at the next match. Got to wondering if the molecular alignment as the bullet hardened would make a difference in accuracy. But, since I face north when casting and all the ranges I shoot matches at you face north I never got around to experimenting with that idea. But maybe I ought to face another direction. Maybe Joe has an opinion on this! :)

This seems like such an easy thing to test for oneself that further hypothetical discussion on it seems useless. I don't think one person who's replied to the weighing bullets threads has said they were able to prove to themselves weighing showed up on the target.   I'm not to sure this would be as easy to prove as it might sound. Casting out of wgt. bullets would be easy, or you could file some off the nose. The difference would probably be so small until you got to some ridiculous variation it would be obivous. But, as a target shooter I would want to know when you get a difference that could easily be covered up by some other condition.

PETE

Attached Files

CB posted this 25 June 2007

PETE wrote:   I'm not to sure this would be as easy to prove as it might sound. Casting out of wgt. bullets would be easy, or you could file some off the nose. The difference would probably be so small until you got to some ridiculous variation it would be obivous. But, as a target shooter I would want to know when you get a difference that could easily be covered up by some other condition.

PETE

Pete,

What you wrote above is exactly the point, it'd be pretty hard to cast some ridiculously out of weight bullets. Next time out just don't weigh a batch of bullets and see if there's a difference on the target. Seems a pretty easy test to me.

We don't normally file our bullets so while it's interesting for conversation's sake it doesn't apply to the real world. If you can cast .30 or .32 cal bullets on demand for testing purposes that vary 1 1/2 or 2 grains you're a better man than me. Bottom line is that during normal casting sessions where you're getting good looking bullets I don't think you'll be able to see a difference on the target. The problem lies in the fact that we all tend to tell new shooters that it's an absolute necessity for extreme accuracy without ever putting it to the test.

Pat

Attached Files

JeffinNZ posted this 25 June 2007

I recently did my 'annual' run of round balls for my .40cal muzzleloaders.  After weighing about 40 of the balls and finding them consistant to the point of being BORING I demonstrated enormous self restraint and refrained from further weighing instead visually inspecting only.

Took a fair amount of self control not to weigh each one though.

Who's a creature of habit?

Cheers from New Zealand

Attached Files

CB posted this 26 June 2007

pat i. wrote:

Pete,

We don't normally file our bullets so while it's interesting for conversation's sake it doesn't apply to the real world. Pat

Since none of us can cast lots of bullets that weigh substantially less than average, and if we want to find out if weight variation affects accuracy, one method is to file some weight off the outside of the bullet-simulating a “hole", and test those bullets for inaccuracy.

That's why and what I did, as has been explained several times here.

It remains for one of the smaller group shooters to file a bit off some bullets and test to see how accuracy changes, or to devise and perform another test.

A test of 5 groups of 5 shots at 100 yards with a very accurate rifle, in the course of other testing, would be very valuable.

Why doesn't one of you do such a test?

Tomorrow I'll test the .1 grain files 22 RF bullets.

joe brennan 

Attached Files

CB posted this 26 June 2007

PETE wrote:   I'm not to sure this would be as easy to prove as it might sound. Casting out of wgt. bullets would be easy, or you could file some off the nose. The difference would probably be so small until you got to some ridiculous variation it would be obivous. But, as a target shooter I would want to know when you get a difference that could easily be covered up by some other condition.

PETE

Pete,

You are so right about other conditions having more of an influence. Those other forces are greater than the force of cast bullet's weight variance, though weight variance is a differential force of it's own.

Segregation of weighed bullets is not so called conventional wisdom, theory, opinion, or old wives's tail, it is sound mechanical design. No one builds a match rifle saying .001” or .002” to center is mechanically close enough, but to achieve symmetrical design as absolutely close to exact as possible. As close to exact as possible cast bullets is a sound mechanical criteria and weight is a good indicator toward a band not filled out completely, or somewhere on the bullet, that can't be measured. Weighed bullets is a constant, not just a self confidence factor..............Dan W.

Attached Files

CB posted this 26 June 2007

Joe,

What more testing do you want me to do than actually compare weighed vs unweighed bullets that I cast in my guns. I don't normally take a file to my bullets or cast bullets with a 2 grain spread so both things don't pertain to my shooting. For conversation they're interesting experiments but since trying to get my new barrel to shoot is a little more important than performing tests for testings sake alone that don't apply to me I'm not inclined to waste time, energy, powder, and lead on something that I've already proven to myself doesn't make a difference.

Dan,

Mechanically weighing bullets makes perfect sense, as does weighing powder charges, getting the ES as close to zero as possible, using only powders that fills the case to the bullet base, and plenty of other things that in theory should lead to better accuracy but in real life experience haven't been shown to pan out. I truly believe most if not all people would find that if they left their opinions out of it and ran unbiased side by side testing they wouldn't find any difference in weighed vs unweighed bullets on the target. 

I'm also going to include something I wrote in another thread for your opinion since it wasn't really addressed where it was.

"Let's say you weight segregate bullets into two groups, 1 batch 200 grains and the other 199.5 grains, what's to say half of the 199.5 gr. group aren't in reality 200 gr. bullets with a 1/2 grain void? Weight segregating makes perfect sense from a logical stand point but is it really helping?"

Like I've been saying all along but getting no where with is that guys who actually shot the w vs uw bullets side by side agree they can't tell the difference, the rest are just going by what seems like a logical conclusion and stating it as fact.

Pat

 

Attached Files

CB posted this 26 June 2007

PETE wrote:  Joe,

 You can also add variaition in pot & mould temp. will affect bullet wgt. All the pots I've used over the years start out varying about 10 degrees from lite on to lite off. As they age this increases to about 20 degrees when it seem to stabilize. I don't know of anything you can do to correct this either.

  Then mould temp. has been shown to affect the wgt. I'm sure we've all noticed that bullets tend to get heavier toward the end of a run. Some tests have been run with thermo-couples attached to moulds and the mould allowed to vary in temp. and the wgt. of the bullets recorded. This mould temp. seems to be the critical factor in bullets varying in wgt. The closer you can keep the temp. the closer your wgt. variation will be.

  Added onto to your reasons it does seem a wonder that we can cast anything like close wgt. bullets. Sometimes some of my casting sessions would make you think I had all the above problems at the same time! :)

PETE

Will changing lead pot temperatures change the weight of cast bullets?

This is an approximation.

Iron/Steel as in bullet molds has a coefficient of linear expansion in temperature of about 11 parts per million per degree C.

Volume~weight of the cast bullet varies as the cube of mold dimensional changes, hotter molds are bigger molds and cast bigger bullets.

A degree F = 5/9 of a degree C, so the coefficient is ~6.1 parts per million per degree F; cubed is ~ 228 parts per million of WEIGHT per degree F.

Or, .023 grains per 100 grains bullet weight per degree F.

So a 10 degree F change in mold temperature of a 100 grain bullet causes a .23 grain ~ quarter grain change in bullet weight. If I did this right.

So, fluctuating mold temperatures will cause significant changes in bullet weight, as Pete said.

 

joe brennan

Attached Files

CB posted this 26 June 2007

I have PMC Match Rifle 22 RF bullets triangular filed with .1 grain and .3 grain filed off the sides. Here's the .1 grain bullets:

Attached Files

CB posted this 26 June 2007

Here are the bullets with .3 grain filed off-.3 grain is a lot. I had to weigh each bullet before filing, then re-set the scale and file. Here's the recorded weights of 30 cartridges in grains:

51.5-1

51.6-2

51.7-3

51.8-5

51.9-4

52.0-6

52.1-4

52.2-2

52.3-1

52.4-3

The average weight is 51.9 grains and the standard deviation of cartridge weight is .228 grains. To put this in perspective, the standard deviation of cast 30 caliber bullets can be pretty easily held to .150 grains; so that .228 grains is A LOT. What do it mean?

joe brennan  

 

Attached Files

PETE posted this 26 June 2007

  Dan,

  Guess I never looked at weighing bullets as being sound mechanical design, but sure do see your point. To me it seems like you have to take all the little “improvements” you can come up with and add them together to get the whole picture of what accuracy is. Each little thing you do might only subtract, say, a 1/16” from the group. But if you get a good barrel and have a good smith make you a rifle that will subtract quite a few 1/16's from your groups. Then all those little things you can do when casting helps to.

  Now there's nothing wrong with “plinking” ammo. I've shot a lot of it myself, but even at that I like to see what that plinking rifle will do with a little work.

 Joe,

So a 10 degree F change in mold temperature of a 100 grain bullet causes a .23 grain ~ quarter grain change in bullet weight. If I did this right.   In actual practice it's probably a little more than that...... depending on caliber of course. For a .30 cal. it might be something on the order of + or - .2 over a run. For the 100 grs. in your example it might be a little less, say + or - .1 gr.

  The thing we have to keep in mind is that as the mould vaires in temp. so does the pot, and off the top of my head I'd say that both will keep “time” with each other. I try to smooth out the mould temp. by casting at the rate of a little over 200 bullets an hour. You have to be very careful in how you regulate things. If you think about it as the mould heats up your casting rythmn will slow since it takes longer for the sprue to harden. So I regulate this by touching the sprue plate to a damp sponge and by having a record of the temp. the mould works best at. Usually about 800 deg.'s covers most.. You can keep a pretty close eye on the mould temp. by how your bullets drop out. If they stick then the mould is a little to hot and I leave the sprue plate on the sponge a little longer.

  Since I keep my bullets in the order cast, more so I can keep count of them, I find that the ave. wgt.s tend to rise and fall as you go along.

  Another thing you have to be aware of that seems pretty consistent is that as the pot level goes down the bullet wgt. goes up to. Not sure why this happens. Any guesses?

The average weight is 51.9 grains and the standard deviation of cartridge weight is .228 grains. To put this in perspective, the standard deviation of cast 30 caliber bullets can be pretty easily held to .150 grains; so that .228 grains is A LOT. What do it mean?   It do mean that the priming compound varies quite a bit, with the powder charge being a close 2nd. In CF primers this is the biggest factor in the differences in weight. The cup and the anvil, for all practical purposes, weigh the same. JUst to forestall yourr next question..... Did the experiment so that's facts speaking and not guesses. :)

PETE

Attached Files

CB posted this 27 June 2007

On 6/27/2007, Model 12/15 BSA Martini, Lyman STS 30X, 50 yards, windy and starting to rain in fits.

Perfect, .1 grain filed, .3 grains filed ammunition.

This gun, like the rest, loves Eley Match ammunition.

I was going to file some Eley Match Red Box, I had the file in one hand and the first cartridge in the other, but a force stronger than I, (and I am enormously strong), kept me from touching that Eley cartridge with the file.

I was able to file the PMC Match Rifle, this ammunition works well in this gun.

Group sizes, leaded edge to leaded edge - .244", all in “

Perfect -.1 gr            -.3 gr.

.433     .473            .353    

.382     .564            .324

.439     1.294            .394

.419     .732            .546

.547     .443            .910

Avg.     Avg.            Avg.

.444     .699            .505

 

Here's the target

joe brennan

Attached Files

tturner53 posted this 26 October 2009

Wineman loaned me a mold, a GB Lee 6 cavity .318 Loverin style going about 174 gr. Mine has averaged 174 gr., with a spread from 173 up to 174.5, and an occasional oddball. This is after visual inspection. Seems to me to be pretty good for a 6 cav. , but without weighing I'd have those oddballs in there, and I'm trying to find some target loads. You guys talk about .5 gr. increments not making a measurable difference, what about 1.5 grs.? These are for my milsurps with iron sights.

Attached Files

corerf posted this 26 October 2009

tturner53,

Personally I segregate into 1 gr groups and load knowing the groups will vary. I mean, I load 221.5 to 222.5 bullets, say a lot of 10 in multiples of 5. Then as I box them, they are arranged in fives, tens, etc. So the cases are sorted after loading. As I pull, I know that my 5 shot groups will weigh the same, from group to group there might be a substantial deviation. I just know not to fire a 6th round from another group, that becomes round 1 of the next group on paper. Seems like I have OCD, but I don't. I am a slob typically. It keeps things organized for me and I have seen the rise or fall of a 2 gr bullet change from group to group. It's in the chrono data very clear. I'd rather have 1601, 1601, 1601, 1603, 1602, than 1601, 1612, 1608... etc. If you have the time to invest, why not do the due diligence... if you have the time or patience

Attached Files

mrbill2 posted this 26 October 2009

When I first noticed the imperfection on the bullet, it was just the size of the point of a pin. Why it caught my eye, just luck. I grabed a lead pencil and poked around the little mark and look what I uncovered.

 

mrbill2

Attached Files

Dollar Bill posted this 26 October 2009

That's why I weigh bullets. When visually inspecting hundreds of bullets, it's too easy to miss something like that. I find the weight inspection more revealing than the visual. We're talking rifle bullets. Weigh them, lay 'em out on a piece of cardboard in rows by weight, and you eventually end up with some sort of bell curve. Drop the high and low end for foulers, shoot the rest for record. With digital scales, it's too easy.

Attached Files

corerf posted this 26 October 2009

I have found that by weighing, regardless of accuracy benefit, that I dont have to look as close to find those voids or round edges. The scale picks 'em out. Thats a pretty big void there. Is that Lyman 210 gr?

Attached Files

codarnall posted this 26 October 2009

Joe Brennan wrote: It has often been stated that with average group sizes well under 1", that weight variation within the feasible range increases group size substantially. However, data to support this belief is sorely lacking, and needed.  

joe brennan Very nice essay!

Actually there are scientific experiments that test the dispersion of voids created at the cg of the bullet. 270 bullets were drilled at the cg with a .00118” drill.  Four three shot groups were shot a 100 yards from the lab test gun.  The bullets were orientated up down left and right  when exiting the barrel.  The four groups all under 1/2” are at 12, 3, 6, and  9'oclock on a circle five  inches in diameter in agreement with Dr. Franklin Mann 's equation published in 1909.   Canting can be bad bad too!----Charlie

Source: "RIFLE ACCURACY FACTS", by Harold R. Vaughn  (Hal)

Attached Files

RicinYakima posted this 27 October 2009

Vaughn's book is required reading for an update on Mann's work. It has been a couple of years since anyone has asked, for the new members, what reading list they should be working on.

Ric

Attached Files

Dollar Bill posted this 27 October 2009

That brings to mind a post by Ed Harris. He had sectioned bullets from a top competitor and found they all had tiny air bubbles, but were all close to the longitudinal axis, so had little effect on the bullet flight. Until (or if) my casting technique improves to the point I can produce such bullets, it would seem advantageous to orient components.

Attached Files

mrbill2 posted this 27 October 2009

Somewhere on this computer while just surfing I seen a picture of a set up where the mold is vibrated while being poored. Don't know if that would reduce the voids or not.

mrbill2

Attached Files

codarnall posted this 30 October 2009

It's my opinion only but I tend to thing impurities in the melt give rise to most inclusions when the temperature, hot mold everything else seems normal.----Charlie

Attached Files

Dicko posted this 18 November 2009

I agree with Pat i's point that very few can show evidence that weight variance affects acuracy, and what seems logical is accepted as fact without proof.   That's not to say that weight might not affect matters, but slight weight variance shares with slight powder charge variance the distinction of being the least important factor.

You'd need a significant weight variance to see it on target and then only at long range.   Some primers vary chamber pressure quite a lot, and because pressure is closely related to MV it would cause significant variance in MV which would have a much bigger effect on grouping than slight difference in bullet weight.  Same goes for case weight, so if you want to weigh anything, weigh your cases.

Of course it depends what is meant by “accurate” and how much variance in bullet weight is acceptable.   It also depends on the rifle.   Walt Berger once told me that the difference between a hunting bullet and a bench rest bullet could hardly be detected in a sporting rifle because even an accurised sporter is not accurate enough to take advantage of the quality of bench rest bullets.

So, slight variance of maybe half a grain will not show up in sporters but it might in a heavy bench rest rifle.   But then all the other factors will have been taken care of as well.   It amounts to eliminating the variables.   And that is one of the only two reasons for weighing bullets, the other being that its the only way to find those with air bubbles.

But I have news about weight variance from the same melt.   First, you'll get bigger variance from two cavities than one because of tolerances.   Second, my rifle bullets are seldom outside 0.20 grains either side of average.   Third, random weighing rarely finds a bullet outside those limits.

As for mould temperature affecting weight, I very much doubt it.   Or alloy hauled out from different depths of the pot.   But I will run a test at two significantly different temperatures with a single cavity mould and see what I get.

Bottom line ?   Weighing is probably a good idea for a match to cull out the odd flyer that might be light because of an air bubble, but otherwise bullet weight and powder charge weight are the least important factors in accuracy.   Within reasonable limits.  Reasonable would be half a grain each way, which should be easy to get with proper casting technique.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Attached Files

RicinYakima posted this 18 November 2009

If you are weighting them anyway, for internal flaws, why would you not drop them into separate cups of 0.1 grains?

Attached Files

billwnr posted this 18 November 2009

RicinYakima wrote: If you are weighting them anyway, for internal flaws, why would you not drop them into separate cups of 0.1 grains? Bingo!!

Attached Files

LWesthoff posted this 19 November 2009

Haven't any of you guys ever read Frank Marshall's article titled “ORIENTATION AND SELECTION: TWO KEYS TO ACCURACY” on page 140 of the NRA Cast Bullet Handbook? Marshall makes a pretty darn good case for weighing bullets for use in competition, and has some (composite) targets made with bullets of various weight spreads to back up his argument. Makes sense to me. I weigh every bullet I cast that survives my initial visual check, and I segregate by weight.

Attached Files

tturner53 posted this 19 November 2009

Just a thought; would it be logical to assume a 1% weight variation would cause a 1% variation in group size? For instance, a 1” group would become 1 1/100” group? Speaking of Frank Marshall, I've been reading a bunch of his old FS articles, that guy is somethin' else. I gotta get that CD. You guys wanna treat yourself to a good time, order some old Fouling Shots. This may be a little corny, but when I'm reading them I get the feeling like I'm...well, I'll stop there, I don't want to make you all cry. I'll just say it's special, makes me realize how much more there is to the CBA than meets the eye.

Attached Files

RicinYakima posted this 19 November 2009

'53,

No, it is not logical to assume a 1% weight variation will make a 1% larger group. If a void, it depends upon where that light spot is in the total volume of the bullet. Farther from the center line of form, increase instability.

Ric

Attached Files

Dollar Bill posted this 19 November 2009

LWesthoff wrote: Haven't any of you guys ever read Frank Marshall's article titled “ORIENTATION AND SELECTION: TWO KEYS TO ACCURACY” on page 140 of the NRA Cast Bullet Handbook? I have. It's why I orient components. I know I can't produce perfect bullets so it just makes sense to me to index everything, for match loads, to minimize the effects of the imperfections.

Attached Files

big boar posted this 19 November 2009

Though I do shoot from a bench sometimes, I wouldn't consider myself a benchrest shooter. Most of my shooting from the bench is to work up, compare or verify a load. I've done the visual/weighing of batches of bullets over the years as we all have and divide them into lots of A(best) or B(minor defect/weight variations). I've surprized myself a couple of times when, shooting groups from the B lot, has given superior or equal target results. This is usually defects of rounded bases and targets were limited to 50-100yds. When I shoot 200yds I've only ever shot groups from A-best lot. Perhaps this is an unfair test but I now toss out fewer defective bullets and for anything out to 100yds I think I'm ok.

Attached Files

Bob Krack posted this 23 November 2009

Lots of good logic here.

The one thing that confuses me is this - 'spose I cast a 500 grain .45 and another of 510 grains, I am lookin' at a 2% difference I think.

Now I cast a 50 grain .22 and a 51 grain I still think I'm lookin' at a 2% difference.

So - if we do decide that weight has an effect, why would I choose .5 grain per projectile difference as the determining factor? Why not 1% or 1/4 % or 2 % (independent of the total weight)?

That is not even considering the difference in speed or rotation rate (twist).

Can anyone here tell me that a 2 or 3 or more percentage difference in weight has absolutely no effect on the accuracy of the projectile?

Bob

Attached Files

LWesthoff posted this 23 November 2009

Bob: Good hypothetical question, but...I cast .30 cal. bullets for match competition - all three styles around 200 gr., and I select bullets from the top of the bell curve, with a maximum weight deviation of +/- 0.2 gr. More often it's a total weight spread of 0.3 gr. That's a maximum weight variation of +/- 0.1%. Applied to your 500 gr. .45 bullet that would be a total weight variation of one half grain. With your 50 gr. mouse killer, it would be too small for me to worry about, but the point I'm trying to make (not very well, I'm afraid) is that a 2% weight variation is far too great to even consider - regardless of the “target” bullet weight. Frank Marshall, in the article I referred to above, was talking about the difference in obtainable accuracy between targets shot with bullets varying 0.1 grain and those shot with bullets varying 0.2 gr., and he makes a good argument - IF you are trying to shoot one hole groups. If you are trying to develop a good hunting load, or a good plinking load, or even a good cast bullet silhouette load, then I think there are a lot of other considerations that enter into the picture. If that's what I was after, I'd still weigh my bullets, but I probably wouldn't be quite so picky.

Wes

Attached Files

tturner53 posted this 23 November 2009

Those tiny weight variations you guys get amaze me. I think I must need to flux more, I can see a little crap in some of my bullets. Typical for me from a two cavity mould is +/- up to 2 gr. on a 200 gr. bullet. Probably need to clean my pot(no, not that pot). Still, getting better all the time. I wonder if when I can get consistent sub-moa will I be content? Or maybe just keep chasing smaller groups? If I recall correctly, the record is .2 something. Fine line between mediocrity and fame. I suspect eventually 100 yd. groups will be meaningless due to inability to measure a difference between competitors. Like Olympic records measured in thousandths of a second.

Attached Files

Dollar Bill posted this 24 November 2009

tturner53 wrote: Those tiny weight variations you guys get amaze me. I think I must need to flux more. I'm with ya, Tim. Until a year or so ago, I only had one casting pot, a Lee 10#. Since I started alloying in the fish fryer and casting from a dedicated pot, my consistancy has improved. Still not where I want to be. Out of 100 bullets, after rejecting visual defects, I still get a 1.5 to 2 gn differential, and I think that is from garbage still in the alloy. I've got a couple hundred #s of WW in ingots, so I'm going to add some tin and flux like crazy before I pour that into ingots. See if that helps.

It's like everything else in this sport. All I try to do is better what I did last time, whether it's in the initial melt stage or on the firing line. Do a little better each time.

Attached Files

Tight Wad posted this 30 September 2010

 

let me weigh in on this topic,ha ha.  I shoot Sierra BTHP 180 grain Match Kings, My gun shoots these best of all. My Hyskore gun rest with remote trigger can shoot a .605 inch group of these bullets at 100 yards summer, winter, rain, or shine. Do not show up to a local gun range with money to bet and I have a box of these in my range bag. It started out that I shopped at Sierra because I live in Missouri and believe in Patronizing business that are (first to last) in my Neighborhood, City, County, State, and Country. Sierra is located 50 miles from Kansas City in a small town named Sedalia MO. The state fair is held in Sedalia which has given me an opportunity to drop by their facility. Sierra is home to the largest underground privately owned testing facility in the world 300 yards. One of the many tests that are conducted on their bullets, before they are offered for sale is taking 5 random bullets from a batch and shooting them at target set at 200 yards.  The total group cannot exceed .625 of an inch. It appears all their bullets go through the same hole at 100 yards and this is  not considered a sufficient quality examination. I write all of this to make one point, if you want to construct an accurate bullet and find out what is important and what is not, ask some one who has done it. Sierra bullet weight control tolerances are +/- 0.3 Grains. It appears varying weights start showing up at long distances, when the energy starts bleeding off.  The shorter the distance the more power, the less the difference.  if you were to take two bullets weighing 20 grains different and everything else being exactly the same, then firing them from the same gun there is a distance that both bullets will go through the same hole, say 25 yards, but the lighter bullet will travel farther being propelled faster, and maintain a higher trajectory than the heavier slower bullet.  20 grains or .5 grains the heavier slower bullet always hits the ground first, this is just physics.   I full well realize some who read this are not ready for this information, and will want to argue, on the other hand there are some nodding their heads right now, if you are nodding your head here is another revelation, Sierra polishes their bullets too.  Smart people learn from their mistakes, truly intelligent people learn from others mistakes.

Some People Invest in Gold & Silver, I Buy Lead & Brass/Steven C. Johnson

Attached Files

Close