Acceptable Weight Variance?

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  • Last Post 27 February 2016
OkeyMaple posted this 16 July 2013

Casting 25:1, 205GR mould, .322 base,  775-800 degree melt. Visual (cosmetic) results are fine. Weights range from 204.4 - 205.6 GRS. For precision  (BR) shooting, does it make sense to segregate by weight  ..........  ie. What would be acceptable weight range?  204.4-204.6, 204.7-204.9, 205.0-205.2, etc., etc. Any suggestions?

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pat i. posted this 16 July 2013

Do a test and shoot some groups using the exact same weight and then shoot some using the extremes. I'm betting you won't find a difference on the target.

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jhalcott posted this 16 July 2013

I personally don't THINK a 5% difference in weight is a big deal in MY shooting. If you are shooting long range(300 to 600 yards) it MIGHT be a factor. MY shooting is plinking at various ranges inside of 200 yards and hunting at the same distances, I USED to be anal about shooting and weighed everything from primers to finihed ammo, powder, bullets and cases included! Every bullet HAD to weigh within a grain and a half of the average weight of 100 castings. I spent more time remelting then shooting! My alloys were checked at work to be exactly the same from batch to batch. NOW I just fill the pot and dump some bullets, IF they shoot good , fine. If they don't I just plink with them till they are gone!

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onondaga posted this 16 July 2013

http://www.castbulletassoc.org/forum/view_user.php?id=7492>OkeyMaple

 The standard I use for match grade cast bullet sorting is 1% of the bullet weight. For your bullet weight that is 2.05 grains. The entire weight range you mention is within the 1%. With that 1% weight matching, the only thing that will shrink your groups smaller is more consistently precise loading, more consistently precise rifle maintenance and more consistently precise shooting.

The standard I use for weight matching hunting bullets is 2% of the bullet weight.

Gary

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RicinYakima posted this 16 July 2013

FWIW, I weight all my match bullets on a electronic scale. I am looking for the “light” ones, less 1% of the mean. Since I already have then weighed by 0.1 grain, I just put them in Dixie cups by 0.1 grain as it isn't any more work than not doing it. I load in 400 round lots, so just start had the heavy end and work down to the light end. May not be any better, but it makes me feel good to have 20 rounds within 0.1 grain in weight. Ric

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John Alexander posted this 16 July 2013

"What would be acceptable weight range? 204.4-204.6, 204.7-204.9, 205.0-205.2, etc., etc. Any suggestions?"

Ask that question of a bunch of CB shooters and you will get a bunch of rules of thumb that different people like to use. These are given in good faith. But none of them indicate that their rule is based on testing. (Maybe they are based on well thought out tests but shooters never seem to cite their evidence.) Pat's suggestion is what I hope people will start doing and then maybe we will find out the answer to your question. All the rest is just opinion or guesses.

I don't mean to be offensive but if we want real answers to this type of question we need to test and report the results in in the Fouling Shot or on line. That's how progress is made.

To follow my own advice I should say that over a period of years I shot hundreds of pairs of groups with bullets of uniform weight vs.either unweighed or light and heavy bullets on the same day from the same rifle and load. I have never been able to see any indication that the averages of the groups with uniform weight bullets were smaller than the groups with unweighed bullets or even with light and heavy bullets in the same group. As far as I could tell weighing bullets is a total waste of time and I stopped doing it.

I haven't weighed and sorted bullets for a very long time. I shoot in CBA competition and based on my testing I don't think I would do better if I sorted bullets by weight.

However, all my testing has been at ranges of 200 yards or less. I wish someone would do similar testing at really long range. The answer might be different but until someone does some logical testing I will be skeptical.

We would all benefit if we did more testing of and reporting on our rules of thumb that have been handed down forever.

John

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Ed Harris posted this 16 July 2013

I agree, variation not exceeding 1% of mean bullet weight is match grade.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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highstandard40 posted this 16 July 2013

I agree with John and Ed, but that being said, I do weight sort my bullets for Silhouette and hunting. I first do a visual inspection for any obvious flaws. Then I weigh them all and cull only those far outside the mean average, most are on the light side and I fear those may have an internal void and cause a flier. The results on 150-200 gr bullets usually yields a spread of +/- a few tenths of a grain. It may not be a needed step but it settles my mind, when I shoot for score or aim at a nice buck, that I have covered every step to produce the best ammo that I possibly can. My opportunities to range test are extremely limited. There is no public range anywhere near me. Otherwise I would do a side by side test.....weight sorted vs straight run.

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RicinYakima posted this 16 July 2013

John,

And where are we going to find a rifle, load and shooter who is capable to shooting the 100 shot groups, without error, to determine what variation is acceptable?

Not me nor my '03 Springfields will be capable of that type of shooting, especially on an outdoor range. You need to ask the “rail gun” shooters.

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John Alexander posted this 16 July 2013

Ric, I certainly don't have a rifle or load that shoots without error and as the nut behind the buttplate I struggle with consistent bench technique not to mention correcting for wind. But perfection isn't necessary to check if sorting by weight (or any other variable) is improving your groups.

I am sorry that I didn't write more clearly. I compared lots of pairs of five shot groups not 100 shot groups. in my enthusiasm I also exaggerated. I should have said a hundred or more not hundreds of pairs.

I always shot at least a pair of groups at any one trip to the range. One with uniform weight bullets and one with either unweighed bullets or the groups composed of light and heavy “culls. Sometime I would have enough for several groups of each and I would always alternate so factors of fatigue, changing conditions, bore condition, etc. would have as much chance of affecting one group of the pair as the other.

I then averaged the groups with weighed bullets and compared it to the average of the groups with unsorted bullets or bullets sorted to produce the worst variation. I found no difference in the two averages. I believe it was reasonable to conclude that my weighing and sorting was a waste of time.

These pairs were shot while I was checking variations in the powder charge or some other variable but both halves of every pair were identical --except for the weight sorting or not. So checking for the effect or lack thereof of weight sorting was during shooting I wanted to do anyway -- sort of a by product.

The rifle and load I was using was averaging about one minute of angle for the five shot groups so with a more accurate rifle and load maybe the weighing would have helped. This was also with 22 caliber bullets. Maybe for larger bullets the dreaded air pockets are more of a factor.

So I am not claiming that my results hold for larger calibers or at ranges over 200 yards or for much more accurate equipment. That is why I would like to see others do some testing to check out the wider array of possible situations. Maybe weighing makes a difference for some situations but we will never know unless somebody systematically tests to find out.

John

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John Alexander posted this 16 July 2013

Highstandard40,

I understand that the temptation to weigh and sort bullets is strong. It is so darned logical -- it SHOULD make a difference.

It also may give confidence as you point out and if so it is useful.

With modern electric scales it isn't the burden that it once was so the time spent isn't overwhelming. But for me it is time wasted.

Last this is a hobby and we can do it anyway we like and most people like to weigh. I am not criticizing shooters who weigh and sort but I am lazy and don't.

I also think we shouldn't tell new cast bullet shooters that they should weigh bullets. Cast bullet shooting is fussy enough without thinking you also have to weigh and throw away some of your hard earned bullets.

John

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highstandard40 posted this 17 July 2013

John, I agree. For the vast majority of bullet casters, weight sorting is a waste of time. The only reason I do it is because I am trying to achieve the ultimate accuracy out of my ammo. In IHMSA silhouette, you can shoot a perfect score if you can keep all your shots inside 6 MOA at 200 meters. But that is just to get to the shoot-offs. Then I am called upon to engage a target as small as 3” at 200 meters......with a handgun. This is scoped of course, but I have only a 6X on my XP100. I have been able to get my XP to group in the 1.2 MOA range with cast, after long and tedious load developement, part of which is weight sorting. The difference is probably marginal at best, but it is a step I am willing to take if it will gain me just one more target per match. The steps I take loading my ammo are far beyond what most people require for an enjoyable day at the range. But the accuracy demands of my sport prompt me to take those steps. It's not for everybody. But hey, I'm retired and I find any time I spend at the loading bench as time well spent. Almost as much fun as range time.

Now as far as my 40 S&W and my 45ACP, I would never bother with weight sorting. Cast, load, shoot, and enjoy.

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billglaze posted this 17 July 2013

I'm entering the “to weigh, or not to weigh” fray with something I found interesting. I hope others do also. Recently, I have been having some success with the Lyman 311299 bullet. With the last batch I cast,(approx. 300 out of 2 cavities) I was getting some results showing promise. (Whl. Wts. with a bhn ~11.) I decided to weigh some just to see how uniform they were. Out of the #2 cavity, (at this time, the only one checked for this particular phenomenon.) I was running along, smugly satisfied that all the bullets checked inside a weight envelope of ~200 gr. +/- less than half a grain. Then, unexpectedly, I came upon one that weighed almost exactly 190 gr. I kept on weighing until I had 10 of those lightweights; it took quite a few bullet weighings to get the 10. I kept the loaded rounds with the lighter bullets segregated from others, and used the same powder charge I used for the “normal” weight bullets of 200 gr. The surprise came in the shooting. Not only was the point of impact exactly the same as the heavier castings, but the grouping was the same size, a tie size-wise with the other bullets. Now, I'm sure that there had to be a reason for the light bullets, most probably because of the dreaded “void” inside, although the bullets checked visually the same as the other heavier bullets. And, the way they're shooting, I find myself reluctant to spoil even one by sectioning it. Does anyone have a potential reason for the lightweights, except a void? I can't think of another reason. According to this, bullets of the same profile, and a full 10 gr. lighter, made no difference. Mystifying.

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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onondaga posted this 17 July 2013

http://www.castbulletassoc.org/forum/view_user.php?id=5098>billglaze:

I have noted ~5 gr heavier with lead splattered on the mold tops or the bottom of a sprue plate. This raises the sprue plate, makes  bullets longer and heavier, but I usually catch that and clean it up pretty fast.

Flash or splatter between mold mold plates can cause fins on the bullets to make ~5 gr heavier bullets. Those defects are easy to spot and then clean the mold.

The combination of a warped or held up by splatter sprue plate plus a flash between mold blocks from inconsistent closure or splatter on the mold blocks could add ~10 gr to a bullet and it could be missed in a visual only inspection. So there is one way to get +10 gr. But, You are getting 10 gr lighter bullets.

Ten out of 300 is very good in my opinion. You might bring that down with increased mold maintenance and casting method modification.  Swirl casting that I have discussed many times plus a larger puddle on the sprue plate when casting will minimize or completely avoid getting casting voids that lighten bullets.

So, if you are getting light bullets with voids, try the classic swirl casting, or if your casting equipment setup will allow,  the Lyman Pressure Casting method with a Lyman bottom pour spout pot and Lyman molds, then pressure casting could solve the problem also.

Gary

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jhalcott posted this 17 July 2013

Bill, way back when I was assinine about this stuff. I noticed the same phenomenom of light bullets. I started to sort them by cast, each throw was set in the line just so! I noted what I had done at each throw, added alloy ,changed molds what ever. It seemed the light bullets were happening when the melt was cooler for whatever reason. Or the MOLD was cooler because I was changing over to another one in the mix.

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jhalcott posted this 17 July 2013

As far as the testing thing goes, I tried that also. I found no real difference in bullets weighed or not IF the other loading steps were consistent! I shot sillywets with several calibers from 30-30, 7TC/U and 45-70. In the “old” days with full footed rams, it was hard to knock over the rams with the 7TC/U and 145/150 grain cast."Head” shots were the norm. I tested lots of rounds on paper out to 300 yards that were not used on silly wets, but on deer and ground hogs. I USUALLY shot 4 groups of five shots. Taking a shot about once a minute or so at each corner of the target. At the end there would be 20 holes in the paper. THEN a new target and load was used. It was easy to see the results when held up to a light. These tests were what led ME to quit wasting time on weighing the bullets. IF one group was bad, it seemed the mold or alloy was at fault. Juggling the powder charge would cause erratic results.

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muley posted this 18 July 2013

I find the light weights that I cast, seem to come when my pot temp get's above 800 degrees. when ,I drop the temp lower the weights even out. I segregate my bullets by +/- two- tenths grain. It may not be needed, but , it makes me feel better. Jim

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Tom Acheson posted this 18 July 2013

Can't resist either!

I started out weighing, looking for the odd way underweight critters in the pile. After awhile I decided to sort them by 1/10th grain. During shooting season I work my way through the collection from lightest to heaviest. The bullets I shoot in the April match won't have the weight as the June match but that don't matter. On match day the bullets are are all very similar in weight and that's probably just a mental thing but I'm sticking to it!

Tom

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jhalcott posted this 18 July 2013

I used WIN. headstamped cases. I would orient the “I” at the top of the chamber, as in I WIN. It did give me a bit of confidence knowing those case were situated in the chamber the same way each shot. Plus the added impulse to win as the cases said! “ANY thing that helps is a plus” according to my old coach!

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Tom Acheson posted this 18 July 2013

Case orientation is something I've heard that some bench resters do. They take it a step further. They put a small punch mark on the mould. Then they check each case on a runout gage and find the thinnest part of the neck (if they don't neck turn). They put a notch on the case rim to indicate that thin spot. Then when seating the bullet, the punch mark is aligned with the notch. Then when chambered, the notch is always at the 12:00 position in the chamber.

With turned necks they still do it but use something other than the notch (to avoid the work of notching) to orient the bullet to the case so they can remember what the “orienter” mark is for chambering if they don't apply the notch.

I wonder if all this craziness helps!

Tom

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hunterspistol posted this 18 July 2013

At that weight bullet, 1.1 grain difference should let you shoot all of them. If you wanted to get really picky, cut it down to a .7 grain difference by losing the lighter 1/4 of them.

Wow, that's pretty good casting.

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R. Dupraz posted this 18 July 2013

I don't know about orienting the bullet to the thinnest part of the neck. But do think that the rest of that craziness does make a difference. I outside turn the necks just enough to make them uniform anyway.

It won't make a 6 into an X but believe the groups have been tighter and more round, which translates into more tens and X,s, since I started using an index mark in the mold to cast, size, load and chamber. I began to see fewer of “what the hell happened to that one” shots over time.

That is when the wind reading factor is left out of the equation, which is a whole nother game.

RD

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muley posted this 19 July 2013

I agree with dupraz, all the other work is for naught, if u fail to read the WIND. Jim

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PredFan posted this 27 February 2016

Hey all:

What is going on if I'm getting very large variation in weights? I tried to mold 240 grain 44 caliber using a lee bullet mold and I was getting weights from 248 to 262 grains.

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TRKakaCatWhisperer posted this 27 February 2016

PredFan wrote: Hey all:

What is going on if I'm getting very large variation in weights? I tried to mold 240 grain 44 caliber using a lee bullet mold and I was getting weights from 248 to 262 grains. Having a VERY low variation in weight indicates that everything is consistent.  There are a number of variables - ALL of which result in weight variation.

THEREFORE, ensure the following (and others will add more):

uniform time between emptying and filling the mould,

uniform mould temperature and temperature of the alloy,

uniform technique in filling the mould.

That is to say, if the temperature of the mould and the alloy are consistent and the technique in filling is consistent, you are a long way into getting uniform results.

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onondaga posted this 27 February 2016

http://castbulletassoc.org/forum/view_user.php?id=9663>PredFan

I found for my casting that one thing improved my weight consistency the most. My pot temperature has the least variance if I drop sprues into a pan and only add them all at once to the pot when the pot is very low while I'm starting a new pot.

Dropping them back in, in groups has a very bad effect on temperature consistency. Dropping them back in, one at a time as you cast,  only works well when your casting cadence is extremely accurate in timing from drop to drop...I mean clockwork accurate or your temperature wanders.

I was not able to see the wild temperature variances till I used a good thermometer or an outboard PID controller.  Without one you just don't see the swing in temperature that causes casting weight to vary. Certainly without one, your sprue melting time is much more important and adding them only when starting a new pot is important for casting weight consistency.

The basics of reading casting quality are only a diagnosis of your work.  You are doing well when you perfect your casting to get consistent complete fill-out and consistent velvety bullet surface indicating good thermodynamics.

Recognize that shiny bullets are small and you are only maximized when they are velvety and sharp. You control that with your cadence and thermodynamics.

Gary

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PredFan posted this 27 February 2016

TRK wrote: PredFan wrote: Hey all:

What is going on if I'm getting very large variation in weights? I tried to mold 240 grain 44 caliber using a lee bullet mold and I was getting weights from 248 to 262 grains. Having a VERY low variation in weight indicates that everything is consistent.  There are a number of variables - ALL of which result in weight variation.

THEREFORE, ensure the following (and others will add more):

uniform time between emptying and filling the mould,

uniform mould temperature and temperature of the alloy,

uniform technique in filling the mould.

That is to say, if the temperature of the mould and the alloy are consistent and the technique in filling is consistent, you are a long way into getting uniform results.

Ah! The old “Practice makes perfect” adage I see.

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PredFan posted this 27 February 2016

onondaga wrote: http://castbulletassoc.org/forum/view_user.php?id=9663>PredFan

I found for my casting that one thing improved my weight consistency the most. My pot temperature has the least variance if I drop sprues into a pan and only add them all at once to the pot when the pot is very low while I'm starting a new pot.

Dropping them back in, in groups has a very bad effect on temperature consistency. Dropping them back in, one at a time as you cast,  only works well when your casting cadence is extremely accurate in timing from drop to drop...I mean clockwork accurate or your temperature wanders.

I was not able to see the wild temperature variances till I used a good thermometer or an outboard PID controller.  Without one you just don't see the swing in temperature that causes casting weight to vary. Certainly without one, your sprue melting time is much more important and adding them only when starting a new pot is important for casting weight consistency.

The basics of reading casting quality are only a diagnosis of your work.  You are doing well when you perfect your casting to get consistent complete fill-out and consistent velvety bullet surface indicating good thermodynamics.

Recognize that shiny bullets are small and you are only maximized when they are velvety and sharp. You control that with your cadence and thermodynamics.

Gary What is causing the weights to always be higher than the weight they are supposed to be? Its a 240 mold but the lowest I have been able to get is 248 grains.

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tlkeizer posted this 27 February 2016

Greetings, Others may have better answers, but what I was told is most molds are set for wheel weights, and most of my lead alloys are heavier. Of course, I may be waaaay off base, but I think that is the reason for heavier bullets and all mine are heavier than mold designation to some degree.

Also, when I get new lead, in a Lee pot I melt a bunch, then pour into biscuit tray segments equally. Melt a bunch more, then pour on top of first pouring, repeating a few times. After cooling, I repeat the process with the “biscuits” to make a large batch of lead that is pretty much the same. Then, when I pour bullets, I use the biscuits in my small melting pot and ladle the lead into the molds, starting to keep the bullets when the edges are crisp. That reduces my variance a lot. I keep like sets of lead separated so when I add a biscuit to the ladle pot it is the same batch as the lead in it already.

I don't use a thermometer, and would surely get less variance if I used one. I get a cadence going with putting the sprue back in the pot as I cast, and as Gary writes the cadence helps consistency a lot, and shoot more so you get more practice in casting (sic).

Hope this helps. Others are a lot more exacting than I, but my goal is heart of caribou, not 10-X. At this point I am meeting my goal at 100 yards with my TD's. Maybe someday I will go back to X's and rings, depends on if my back will ever let me shoot prone again.

TK

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tlkeizer posted this 27 February 2016

Greetings,

R. Dupraz,

Wind? South Dakota?

Have fun, hope your new year is shooting well.

TK

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R. Dupraz posted this 27 February 2016

Hey Terry:

The temp hit 74 today with 0 wind. Nicest day so far. But wouldn't you know it, the club Pres. thinks he's an instructor and has the range tied up all afternoon teaching a “carry gun class". rah, rah.

Check your PM box

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