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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What difference do bullet defects make? Not much if the range is short and/or the velocity is low. if you are shooting at longer ranges (100+ yards) and the velocity/RPM is higher bullet defects can make a huge difference in accuracy.
LMG
Concealment is not cover.........
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If the bullets are equally “flawed” around the whole bullet, and the diameter is correct, and the base is uniform, the effects could be minimal. Bullet weight does impact longer range trajectory though, and could cause erratic points of impact. I totally disagree with Mike Venturino that flaws are immaterial and that you can shoot anything you get out of the mould. He's primarily speaking about handgun bullets I believe, but I think his performance standards for most bullets are far below my own. In the same issues of whichever magazine he's working for, you can see him get really fussy over his black powder rifle casting, so I know he knows the difference.
My standards are the same for any bullet I make. They need to be of the highest quality I can produce.
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My standards are the same for any bullet I make. They need to be of the highest quality I can produce.
We are on the same page, pride of workmanship has a lot to do with what I keep and what goes back in the pot.
Guys that love to chronograph, keep saying the small SD's make smaller groups, yet I have never seen that on the target. Some do, but some don't make smaller groups. Same idea, what you think affects your outcome.
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I inspect under a 3X magnifier that has a quarter-sized 6x magnifier in it. With bright light. On a towel I put a bunch of bullets, and push each, point down, along with my finger, so the bullet rolls 360 degrees, as I inspect it. There are NO perfect bullets under 3X magnification. Some are clearly rejects. As the defect size diminishes, the likelihood that I'll reject it goes down. Yet every bullet has some flaw, no matter how tiny. I find it helps me to consider the whole area of the bullet, visible, at the flaw place. A teeny flaw represents a teeny percentage of the area. Like John, I've shot a lot of rejects into small groups. I just finished putting gas checks on a batch of rejects that I'll use as foulers. I find that I need to shoot at least 10 careful shots before going to the record target, and use these foulers to get settled. So, I don't know if defects matter, or how big the defect has to be to matter. Or how to express the size of the defect in what units. Maybe we need a unit of measure of defect. Since I find it easy to cast defective bullets, we could call the unit the joeb. Any bullet with a defect greater than 1 joeb shoots less accurately than those with a lesser defect. As the moving language has given us: “Just saying”
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What difference do bullet defects make? Not much if the range is short and/or the velocity is low. if you are shooting at longer ranges (100+ yards) and the velocity/RPM is higher bullet defects can make a huge difference in accuracy.
LMG
LMG
I suspect your first sentence is right. Any way it matches my test results.
Do you have any numbers to go with your statement that defects make more trouble at at longer distances? A certain size wrinkle or a certain radius rounding of the sharp edges will make a bullet hit about ___ inches or feet from the group center in at 600 yards? What rotation speed will start to cause trouble? The bullets in my test reported in TFS #213 were rotating at 126,000 rpm so it must be higher than that.
Does anyone know of any testing that answers the above questions or even indicates that long distance and/or high RPMs magnifies the effects of defects? i would really like to see it since I have heard both stated as fact for a long time. I have tried to find where these facts are established and haven't yet.
John
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John, I look at a lot of these statements that should be prefaced by “well, it only makes sense” or “well, everybody knows that that's the way it is.” And, I admit that many times, it only makes sense, or, in fact that IS the way it is. After all, a bumblebee can't fly, and, if God wanted man to fly, He'd have given us wings. Which he did, for Icarus, who, if you recall, came to a rather sticky ending.
I've loaded bullets that I figured would make foulers, and, when fired these defective bullets went right where they were pointed, I've loaded beautiful stuff, that just didn't shoot well; in a shooting session a few days before, they shot well. Same powder, identical in every respect that I could check. I still don't know why this stuff did/didn't shoot well.
And, as I sit here writing this, I still can't pinpoint the reasons for good/bad. And, if Joe, who has a tighter statistical hold on this subject than anyone else I've ever seen, well, if Joe can't quantify it, I'm not too sure it can be done. At least in Dr. Mann's lifetime and probably mine also.
But, I still don't intend to quit trying. It's too much fun!
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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Jacketed rifle bullets are more accurate in my 308 NATO chambered Remington, even with it's loose .311 diameter free bore and long jump to rifling. Is it because the jacketed bullets are more perfect and deform less when fired?
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Opinion: nope because they are about 15,000% harder than lead.
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Joe, I like the idea of using joeb as the unit to indicate the degree of a defect. Figuring out how to measure joebs would be tough, maybe impossible because there are different types of defects and I can't imagine how to quantify a wrinkle.
I discussed that problem in my article and proposed using photos to show levels of defects. The defects in my photos are wrinkles (we would also need at least a rounded edges and base bumps as two other categories.) My tested “reject” bullets had pretty hairy wrinkles yet shot slightly better than the good bullets so they would have to be less than 1 joeb -- maybe we could call them .8 joeb grade.
Even the results of that one test could be used to offer useful advice to a new shooter having trouble eliminating wrinkles. I think showing my wrinkled bullet pictures and advising him that if the wrinkles don't look worse than these pictures they will shoot OK might be useful information.
Or we could give advice by description. Rounded edges -- gas checked bullets will probably shoot OK unless the bands aren't full diameter (good if smoothed by the sizing die) and unsized gas checks don't fall off. I'm not sure that this statement is true but we could test and find out.
These proposed ideas may sound strange but I think some such approach would be better than telling a beginning CB shooter that the bullets should look perfect which is what happens now. That statement probably isn't true but it could discouraging to a new shooters learning to cast.
John
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On the fence on this one. Not so much the testing of the good, the bad and the ugly at long distances. But more of an inconsistency at the bench when we experience the “this load shot good a few days ago but today it stinks” conclusion. We need to look beyond the so called inconsistency of the quality of the bullets and look in the mirror and convince ourselves that our bench technique is repeatable day after day. Failing that bullet quality takes a way down the list second seat.
Tom
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Life is too short to compete with imperfect bullets. The easiest variable to eliminate, particularly in the PB class. If the base is good, the bands square, and no wrinkles, they go into my score box sorted into 1 gr weights. I'd rather spend my time doping wind and mirage than wondering if that “marginal” bullet cost me that 10 or X. C'mon, a glance will tell the tale, if it is not good in your heart of hearts toss it back into the reject can.
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Well from the jacketed world, try a bag of 147 grain M80 pulled from 7.62x51 NATO cartridges. A few blemishes but not too bad, weights however vary by +/- 2 grains. Load them randomly and they have about 4 MOA at 100 yards from a M1903 A3 with iron sights, shot prone with a sling. Sort them into weight groups and you can maybe get to 2 MOA. The control would be to not know what I was shooting (If I know their better maybe I shoot better?). The same rifle in the same conditions shoots well sorted cast, fitted to the throat about 2 MOA at 100. A factory modern rifle, with a scope and bench rested might make everything tighten up but I believe the trends would continue.
I am with Ric, if you make them, make them as good as you can and you will have better accuracy.
Dave
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Well said Tom. Folks go to great lengths to place the blame on small defects or this powder, that primer etc. All to get around the obvious, they have poor technique! No amount of fastidiousness in bullet prep. will overcome personal inabilities. That being a big part of why I shoot plates, gongs, and beer cans instead of benchrest targets. lol Gp
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Early in my association with the CBA I read some posts on this subject so decided to try my own test.
After a few of my first casting sessions I weighed several hundred bullets. I was able to assemble two sixty bullet test batches. Each batch had 30 bullets in the middle of the weight range, 15 of the heaviest bullets, and 15 of the lightest bullets, slightly less than 4 gn spread from heaviest to lightest. I shot five shot groups at 100 yards alternating between groups with the “perfect” bullets and groups with either two heavy/three light or three heavy/two light. In the end the “perfect” bullets averaged 1/4” tighter groups (1.24” vs 1.52").
Coincidentally, my first win was in an informal match shooting groups at 300 yards. The margin of victory was 1/4".
Of course as always there's “the rest of the story".
As anyone should be able to tell you (though many can't) for the results of any experiment to be valid they have to be repeatable. Through the summer the second batch of test bullets sat in a box while I prepared for matches and learned more about casting techniques, shooting techniques, etc etc etc. Finally on a reasonably nice December day I headed for the range with the second batch of bullets. I have no idea why but this time I could barely muster groups around three inches and the most charitable way I can put it is that I was unable to validate my earlier experiment.
In the meantime I have learned to cast more uniform bullets, use more uniform pressure when sizing, work with seating depth, etc etc etc. Even so, as the winter gets longer and colder, when some of those “honeydo's” come along, I may find it useful to have a large batch of bullets that really need to be sorted..>
John Carlson. CBA Director of Military Competition.
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I'm in the camp with Tom, gpidaho and John C. The human factor is rarely added to the mix and in my opinion should always be at the top of the list of why thing go right and then go wrong the next time out when everything else is the same. I have since quit worrying about bullets, powder charges, loading procedure etc, etc, etc,---. Any more I concentrate and continually struggle with consistant bench technique and the fundamentals of marksmanship. Over time, I have learned how my rifles shoot with the loads I use. That is the constant. My application of technique and the fundamentals are not, on any given day. And as far as casting bullets go. I figure that as long as I am going to spend several hours and maybe days making bullets, they might just as well be as good as I can cast them and then let it go at that. Because I have also learned that the one great variable in all of this is me.
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Now I remember. The memory is the second thing to go. 3.5 damaged bullets - See attached file below.
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What difference do bullet defects make? Not much if the range is short and/or the velocity is low. if you are shooting at longer ranges (100+ yards) and the velocity/RPM is higher bullet defects can make a huge difference in accuracy.
LMG
LMG
I suspect your first sentence is right. Any way it matches my test results.
Do you have any numbers to go with your statement that defects make more trouble at at longer distances? A certain size wrinkle or a certain radius rounding of the sharp edges will make a bullet hit about ___ inches or feet from the group center in at 600 yards?
What rotation speed will start to cause trouble? The bullets in my test reported in TFS #213 were rotating at 126,000 rpm so it must be higher than that.
John
There is indeed and RPM Threshold where accuracy goes south due to adverse affect increased RPM has on the imbalances (what defects in the bullet cause). With the ternary alloys we commonly use and the usual fast to medium burning powders the RPM Threshold will generally fall between 120,000 and 140,000 RPM. The things that push the RPM Threshold up are better bullet designs that fit the throat, better balance of antimony and tin in the alloy, less defects in the bullets (consistent bullet weight and shape), consistent loading techniques, a proper lube, a slower burning powder to lengthen the time/pressure curve and numerous others. If you do everything right you can push the RPM Threshold above 140,000 but at some point (the faster the barrel twist the sooner) you will cross the RPM threshold and accuracy will go south very quickly, especially at longer ranges as non-linear group dispersion occurs.
Does anyone know of any testing that answers the above questions or even indicates that long distance and/or high RPMs magnifies the effects of defects? i would really like to see it since I have heard both stated as fact for a long time. I have tried to find where these facts are established and haven't yet.
There are several threads on the CBF and the NOE forum answering that very question(s). Considerable work has been done pushing cast bullets of .30 caliber to higher velocities by pushing the RPM Threshold above 140,000 RPM. This has been done with 10 and 12” twist barrels using the .308W and 30 XCB Cartridges. The .308W and 30 XCB cartridges with 14” twist barrels has also been used very successfully pushing the Lyman 311466 and the NOE 30 XCB bullet to 2600 fps while maintain 1 - 2 moa accuracy to 300 yards with 10 shot groups.
A couple of us have pushed the ternary alloyed bullets to 3000 - 3100 fps with some success. However with my 30x60 XCB cartridge in a 16” twist barrel I can consistently hold 1 - 2 moa through 300 yards. I recently shot a 20 shot group at 300 yards that stayed very close to 2 moa with a velocity of 2900 fps. The first five shots were in 1 moa and the first ten shots were in 1 1/2 moa. A 20 shot test string is admittedly difficult at 100 yards let along 300 yards. I am currently still experimenting to improve accuracy.
Given the fact that most “defects” in different bullets from the same casting will not be identical in shape, weight or location on the bullet the centrifugal force will act on them differently. Therefore it is impossible to say they will hit “X” distance at 600 yards from the center of the group. However, there are formulas in several ballistics books that you can compute the effect a consistent defect in your bullets would have.
However, I don't find I can cast consistent defects so I don't bother with such mental strain. I cull the defects as best I can by visual inspection (pretty much the same as joeb does with a magnifier) and by weight sorting.
LMG
Concealment is not cover.........
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I fall into the group that says, “why shoot bullets that don't look or weight well, in matches"
I shoot PB bullets at 200 yards and while I can repeat good results, I can't repeat them every time. Wind drift is the highest at the velocity range for PB (14 - 1500 fps) and I chock it up to that and me missing a condition.
I keep some imperfect bullets to use as foulers and they will almost always shoot into the same group, after the barrel is fouled BUT, I can't bring myself to shoot them into a record, match target.
It maybe interesting that they can do that but, why do we care?
Frank
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"1 - 2 moa accuracy to 300 yards with 10 shot groups."
I don't think that the above is really considered accuracy if measured against CBA, ISSA or ASSRA match shooting.
You gotta do better than that to have any relevance.
Mel Harris (Roseburg, OR) gets groups of 1/3 to 1/6 that at 158K rpm, with a 212 gr bullet.
Frank
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Wineman and Carison,Thanks for contributing results of actual shooting tests. We need more such data. It is interesting that the max wt. variation was about 4 grains for both bunches of bullets yet weighing reduced group size by a spectacular 50% in one case and only 16% in the other?
Joe,Thanks for all the data. I tried to struggle through it and if I understood at least one part of it indicated that filing .2 is not likely to hurt accuracy enough to pick up in the number of groups a rational person would be willing to shoot.
Tom,I agree with you and the others that the most important action is at the bench but that doesn't mean we shouldn't try to understand what counts and what is just a waste of time in making the ammo. The whole picture is what makes it interesting.
John
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