When do Bullet Defects Make a Difference?
In the thread “Casting with Lyman Molds” Joe Brennan recently mentioned that he had 40-50 rejects in casting a batch of bullets and that he didn’t know why. Joe says he sorts under magnification so that started me wondering how bad those bullets were and if they would have shot just as well as his “perfect” bullets.
When I started casting I used to get a lot of less than perfect bullets and on some days I still do. Being a depression baby, I don’t like to throw things way and when I got curious and shot the “rejects” against my “perfect bullets” they seemed to shoot just as well. I reported on one such experiment with badly wrinkled bullets in TFS #213 in which the wrinkled bullet’s 5-shot groups averaged .78 MOA and the good bullets averaged .82 MOA. I have tried similar tests several times and haven't found a difference as long as I don't shoot the really gross defects -- parts of a band missing etc.
Joe rejected only about ten percent and throwing away ten percent isn't too painful even for me, so maybe this issue doesn't make much difference to experienced casters. But for beginners that rejection rate may include most of their bullets if they believe that any little wrinkle or slight rounding of sharp edges, or bump on the bottom must be remelted. And that’s what we usually tell them because we don't know ourselves. That may be one of the reasons that beginning casters get discouraged and quit. Early success is important in sticking with a new hobby. If we want more CB shooters we should avoid discouraging them unnecessarily.
What do we know about the importance of defects? I think not much. I hope others, out of curiosity, will compare how their rejects shoot compared to their “perfect” bullets and share their results. We have been at this business for several hundred years and really should know more about the importance of defects by now.
John
How Perfect Should a CB be?
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After thinking about the unexpected results of my test above where there was no significant difference in accuracy between weight sorted bullets and bullets that varied by 0.5 grains, it occurred to me that there might be more useful information in the groups.
If group size really did increased with the amount of weight variation in a group (the conventional wisdom) then maybe the best way to detect the effect of the weight variation is to measure the vertical dispersion of the groups instead of the extreme spread. I think that shooters assume that weight variation affects vertical dispersion.
I speculated that maybe a bunch of groups even with the same average extreme spread (as above) could still show the effect of weight variation in the vertical measurements of the groups.
I retrieved the three targets and measure the vertical dispersion. Alas, the average measurement didn’t support my speculation.
Average Vertical Dimension of Groups
Uniform weight bullets,(range in weight 0.1– 0.2) --- 0.28”
Varied weight bullets (range in weight 0.5+ grains ) - 0.19”
I don’t believe anyone would claim that weight sorting bullets caused more vertical dispersion, but there is no hint in these 12 groups that it reduces vertical dispersion.
Summary
1. There was no significant difference in accuracy between bullets that varied by 0.5 grains and bullets sorted to 0.1 and 0.2 grains.
2. Vertical dispersion was not reduced by reducing the range in bullet weights within the groups from 0.5 grains to 0.2 grains.
John
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I should have added one more comment to the description of my test's above.
Of the 60 record shots fired one was disregarded I called it out when shot. It was the only shot that made it's separate hole. It would have made one of the groups of uniform weight bullets considerably bigger. A two oz. trigger takes some getting used to.
John
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Squid Boy,
I agree, shooting is to some extent a head game. This is most easily understood by serious offhand shooters where the the head is the most important part, less so in shooting a rail gun.
I think that much of what accounts for the day to day variation you mention, in addition to the head thing" is two things. One is that most shooters refuse to acknowledge how much groups vary from one group to the next even when all conditions internal and external are the same. "My rifle will shoot one inch groups all day". It won't. If you shoot five or six groups in a "day" it is very likely that one group will be twice as big as the smallest even if the ammo is as perfectly uniform as possible. Some think this principle doesn't apply to accurate rifles. The strings of four 5 shot groups above the average ratio of largest to smallest group was 1.6 and four groups isn't a long string.
The other reason is, of course, factors we don't know or can't control. Mysterious changes in bore condition, weather, etc. And we will never know until we start experimenting to try and find out. We have good evidence that we won't solve this problem by making bullet weights or neck tensions even more uniform.
John
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John, I have seen the exact results you describe and wonder why. I have tried all sorts of voodoo and still see variation. One day a near one hole group and the next not so much. I am making the best ammo I can and this is why I believe some of it is a head game, hence the idea of it is just as important as what you do. At least to me. Plus I just flat out enjoy tinkering with this stuff and never want to stop till I am cold and stiff. Great forum. Squid
"Squid Pro Quo"
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Here is the rest of the story.
I saw the box of Berger bullets with a substantial range of weights as an opportunity to get a better idea of just how damaging to accuracy variations in bullet weight really is. To get the most severe test possible I saved all of the bullets on both high and low ends of the distribution and did preliminary zeroing and crude load work up with the ones in the middle. After zeroing the rifle, I first tried a load of 12 grains of 4227 to produced MV, similar to a lot of CB velocities. This averaged 5 shot groups of approximately 0.5 moa. Since I believed that both the rifle and the bullets were capable of better accuracy, I then tried 24, 25, and 26 grains of H322, somewhat closer to the hot loads many JB benchrest shooters use. After this preliminary shooting I had 64 bullets left.
From the 64 bullets I was able to select 12 groups. Six with bullets that varied no more than 0.2 grain, (three of the six with bullets that all weighed the same scale reading.) Although the other 34 bullets had a weight range of 0.9 grains, my best efforts could only sort out 6 groups that had a range of at least 0.5 grains. A couple of groups had a greater range.
The rifle used was a 6PPC with a Kelby action, a Krieger barrel, a 2 oz. Jewell trigger, and a typical benchrest style fiberglass stock, similar to many CBA Heavy or Unrestricted class rifles but weighing under 10.5 pounds with a 36X Weaver scope. Unfortunately, my front rest’s bag was for hunting rifle stocks but by stretching it out of shape it sorta worked for the 3” flat forearm. The friend I bought the rifle from said it would only agg. .25 moa on a good day with the best loads so was building a better one.
Without going into details, I used my limited brass supply to I shoot two groups with “good” bullets and two groups with bullets that varied at least 0.5 grains on three different trips to the range using loads of 24, 25, and 26 grains of H322 on successive days. Wind flags were not used but conditions were unusually good for the high desert with winds mostly from 10 to 2 of never more than an estimated 15 mph. All were shot from 100 yards, the limit of our range.
There was no significant difference in the size of the groups with the three powder loads. On one day the good bullets shot slightly better and on the other two the bullets with the .5 grain range in weight shot slightly better. The average for the six five shot groups with uniform weight bullets was 0.33 inches. The average for the six groups with the 0.5+ grain range in weights was 0.32 “.
Draw your own conclusions or ignore as it suits.
John
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Lots of opinions, quotes from favorite gurus, statements of personal philosophy. No test results.
Some of that extra time mentioned by 4 in 1 would be more than enough to run some simple tests. That might run the risk of learning something we may not want to know.
I have no interest in trying to convert those who choose to treat CB shooting like a religion and believe by faith what they want to believe, no matter the evidence. It's a hobby after all. But please don't tell beginners, more casual shooters, and hunters they have to do things that make CB shooting a lot more work unless you have evidence. If it's too much a PITA they may just go away and if enough do, so will the CBA.
Squid Boy has a excellent point, but his point has to do with your feelings, lucky cap and rabbit's foot stuff, not physically reality. However, feelings (confidence) may help you win a match so shouldn't be ignored.
John
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I am late to this dance and a lot of great information being laid out. For what it is worth I think that whatever you do that makes you THINK you have the best bullet/ammo/gun on the line is worth it. Thanks, Squid Boy
"Squid Pro Quo"
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I'm in the camp of making the best I can and shooting the best I can make. I've made a lot of jacketed bullets, you go through the whole process, and you never know what you have until they are done and shot. And if they aren't good, it's all a waste. But if you cast a bunch of bullets, then look them over, weigh them, cull what you don't like, and toss those back in the pot. You've lost nothing but some time.
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Want to shoot better scores? Practice more!
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The "Speaking Frankly" 30-06 article in the Lyman CB manual has volumes to say about perfection of cast bullets. Only a careful sorting of bullets was going to be enough for Frank. Lesser bullets had their place, but only for practice. Really imperfect ones went back to the pot.
However, a recent test showed that the shooter has more to do with accuracy than does the bullet. I matched jacketed bullets at the same velocity as cast and my scores were not any higher. Seeing the sights and holding steady had more influence than did the individual bullets. Just my two cents.
Dave
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And only shooting the top 1/3 of the weight segregation. Sorry, can't prove it, don't have five 5-shot groups to show.
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There are a lot of people in the world who don't follow anybody else's procedures. As they have found, you might also if: while weight segregating, you also diameter segregate. That has produced some very interesting results in the lowly 22 Hornet cartridge.
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I posted this 13 January 2016 (pasted from above.)
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While packing up some things to ship to Oregon I ran into half a box of Berger 6mm bullets. In a fit of curiosity I weighed them. While about 90% of them were evenly split between 65.9 and 66.0, a couple were light at 65.8 and a couple were heavy at 66.1, no matter how many times I reweighed them. This is a range of 0.4 grains, or about 0.6%
The common practice of many CBA competitors involves weigh sorting their 200 + -- grain bullets to 0.1 grain or about 0.05%. This is ten times as picky as Berger. Or put another way, if a lot of 200 grain bullets ranged in weight 1 grain (horror) they would have the same weight uniformity as my box of Bergers. The reason I can't get mine-run bullets to shoot worse than bullet of essentially the same weight is apparently because I cast too uniformly. I suspect most experienced casters do as well. Of course, the Bergers could just have been having a bad day. I think I have another box bought years later somewhere and will dig it out and see if those are better.
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OK, so it took 5 years to get back to this. I didn't promise speed or lack of procrastination.
When I weighed a few of the Bergers in the full box, instead of being more uniform than the ones that varied by 0.4 grains, they were worse, much worse. This inspired me to weigh each one of the 100 bullets.
The results produced a frequency vs. weight curve heavily skewed toward the heavy end, just as cast bullets often are. The weights varied from 64.8 to 65.7 for a range of 0.9 grains, or 1.4 % of the average weight. To put this in perspective, this is approximately 28 times the range CB shooters allow when they sort to 0.1 grain. And 14 times as much as those who choose to live dangerously and sort to 0.2 grains.
If the percent weight range of CBs need to be sorted to at least 0.1% as is common practice then it seems unlikely bullets whose range is 14 times the percentage their average weight will shoot well. If so, how does Berger manage to sell the darned things.
[Note: Before I create an unfair impression -- I have weighed other Berger bullets as well as other brands of match grade jacketed bullets and usually find that the range in weights as a % of average weight is much smaller and sometimes amazingly small. So this box may be unusual. However, some of my other samples of JBs that are expected to shoot 0.5 moa or better out of the right rifles also wouldn’t meet the uniformity that many sort CBs to.]
This post is getting too long and I am running out of time this afternoon so tune in later (hopefully not five years later) for more.
For those of you who weren’t on the forum five year’s ago there are lot of interesting posts above if you are interested in what is needed and what isn't for CB accuracy.
John
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It does make weight sorting seem sort of redundant but the other side of the coin is that I'm willing to bet that the winners using these bullets are probably weight-sorting them also. Probably other criteria to meet their own personal specifications also. (Checking ogives, perhaps?)
Just wondering--no evidence either way--strictly an itchy curiosity-bump.
Bill Bill,
Well maybe, but i read Precision Shooting for twenty years until they went belly up and I can't remember among all the crazy sounding thing those fanatics to to get an edge one mention of weigh sorting bullets.
I also have several JB benchrest books and don't remember it being mentioned. I wonder if Tony Boyle recommend it in his book?
John
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John, About 15 years ago at a jacketed bullet bench rest match I was talking with a guy who made match grade jacketed bullets I asked him about weighing bullet. He said check weigh occasionaly. Did not say just how often. A couple of competitors were shooting his bullets and doing very well. Aggregates at .2 MOA. He also told me something that I have never heard or read about. Some electonic scales will develop a memory.
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just a thought ... but weight variance in pressure formed mj bullets are probably core length...and not likely to affect concentricity ( form/cg ) ...
wheras we obsessively weigh castings to find voids which ” do ” affect form/cg .
right guys ?
or not very much .
ken
oh, i bot some pretty mj bullets once that shot 3 moa in my accurate 222 . looked fine . all gone now, can't section them .
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It does make weight sorting seem sort of redundant but the other side of the coin is that I'm willing to bet that the winners using these bullets are probably weight-sorting them also. Probably other criteria to meet their own personal specifications also. (Checking ogives, perhaps?)
Just wondering--no evidence either way--strictly an itchy curiosity-bump.
Bill
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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Bill, It is interesting. It is especially interesting if other Berger bullets vary .6 % in weight. (I will try to the Berger's in an unopened box that I have and see if the ones I weighed were non representative.)
The reason it is interesting is that it is over ten times the weight variation when we weigh sort 200 grain cast bullets to .1 grain (.05 percent). Does this sound like evidence for weigh sorting to .1 grain? Not to me.
John
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A good friend of mine, who shoots Bergers said that he recently checked a box of .30 cal. which he shoots in his 30 BR, and found 4 different ogives in the same box.Apparently they all shot well at the 100 yd. stages (didn't ask about 200 yds.); the Bergers are what he shoots all the time; he couldn't be too disturbed, or he'd go to something different. BTW: he's always on top, or near the top of the list. Just thought it might be interesting. Bill
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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