An accuracy test for Joe B

LMG wrote: RicinYakima wrote: John,

The only conclusion I have is that five 5-shot groups are meaningless, except for the very grosses of differences. However, completeness of form, good fill out, seems to at least equal to matching weights. Therefore, I will look more closely under the magnifier when sorting bullets, just for luck :)!

Ric I certainly concur with Ric, 5 shot groups are meaningless.  That's not what he said. ONE set of five 5 shot groups doesn't prove anything, but can suggest a lot. When I screwed a new-to-me 22-250 barrel on an action and shot it with a load that shoots averages under 2", and it shoots a 3.071” average, that ain't meaningless. Repeated sets of 5 shot groups will get us closer to proof. I have been conducting extensive testing of high RPM cast bullet loads in various cartridges in various rifles with several different cast bullets.  I have been using 10 shot groups as the norm at 100, 200 and 300 yards.  In each and every instance the visually inspected and then weight sorted bullets always shot more accurately when side by side comparisons are done with non visual/weight sorted or just visual inspection bullets with the same load in the same rifle.  The difference in accuracy is much more prominent at 200 and especially at 300 yards.  Show us the groups, or at least tell us the numbers. Allegations unsupported by data neither prove nor demonstrate anything. A load that is developed and is found acceptably “accurate” at 100 yards is all to often presumed to be also as accurate at 200 yards.  Many times that is the case but many times it is not. Larry, where is the data? How many rifles, what calibers, how many groups? In 55 years of shooting I can remember only ONE case where a rifle shot well at 100 yards and not well, with the same load, at 200 yards. This was a H&R Buffalo Classic 45-70 that shot ~ maybe 1.25” AVERAGES at 100 and did poorly at 200. I always suspected that it was on the ragged edge at 100, and that some development would have brought it around. I've heard the tune about 100 yards accuracy falling apart at 200 yards,  never saw another case. The ASSRA guys like to talk about the 100 yard setup that goes to pieces at 200 yards. I asked for years if anyone saw it with a ~ 200 grain bullet in 32-40 and ~ 14.5/IMR4227. No stories, and never heard one of them claim it.

 All too often the 200 accuracy is abysmal compared to the lessor range 100 yard accuracy.  There is a reason for those “not” cases but I'll not get into that here.  Suffice to say if you are going to shoot matches at 200 yards then load testing should be done at that range.  In doing so we find loads developed for 200 yard accuracy and then used at the 100 yard range the moa accuracy will almost invariably accuracy to be as good if not better than it was at 200 yards.    An example of a recent test; I usually cast between 400 and 500 bullets at a session using a 4 cavity mould.  After visual inspection where any defect/flaw is cause for rejection That usually eliminates 20% +/-.  I then weight sort into .1 gr increments.  I use .1 gr increments to judge the “bell curve” of the weights is consistent with that bullet cast of that alloy.   If the visual and weight sorted selected bullet bell curve is as expected I then do the following; I reject the very few at the top end that are “over weight".  I also reject those that are under weight. What does this mean? Do you reject all below the average? What low weight bullets do you reject? What are the average weights from each cavity? Do you segregate by cavity? Bullets cast in different cavities have different average weights. I have data showing this.

 With #2 alloy in the 30 XCB bullet (NOE 310-165-FN) I was usually ending up with about 60% of the bullets cast as being acceptable for HV (2900 fps) longer range shooting (300 yards).  The standard deviation of bullet weights is around .15 grains. That means that 99% of the bullets cast, that pass the visual inspection, will weigh the average +/-.45 grains. An experienced caster should accept ~ 90-95% of the visually acceptable bullets, and the visually acceptable should be ~ 90% of those cast, so ~80% of the bullets cast should be acceptable. Are you mixing up weight by cavity with total lot weight? I also have found that segregating and shooting bullets in .1 gr incremental lots was not showing any accuracy improvement at 100 yards over shooting bullets with a weight range of 157.8 - 158.5 gr.  Previous to this and another series of recent testing I had been using bullets of that weight range because they performed very well at 100 yards and appeared to do as well at 200 yards.  However, at 300 yards there would be 1 or 2 and sometimes 3 flyers in every 10 shot test group that opened the group up from what should have been around a 3.2 - 4” group to a 4 - 5+” group.  Obviously something was still wrong with a small % of those bullets.  Time to find out what.   I then loaded up eight 10 shot test strings of the same load with the only variation being the bullets in each test string were equal in weight to .1 gr.  The eight 10 shot tests each increased the bullet weight .1 gr from 157.8 gr to 158.5 gr.  The rifle used is my 30x60 XCB rifle with a Broughton 31” barrel with a 16” twist.  By CBS rules it would fall into the “Heavy Rifle” category. At the completion of the eight 10 shot test strings at 300 yards I measured the groups and graphed the results for a better “visual” of what was happening.  As we see it was the bullets at the lighter weight end that was causing the “inaccuracy.  The bullets of 158.0 - 158.5 gr weight essentially gave equivalent accuracy. Nope. You've got one test of 8 ten shot groups. You've proved nothing and not even suggested much. Borderline meaningless. That raised the next question; How would a "lot” of bullets with a weight variation of 158.0 - 158.5 gr shoot?  Well, in a previous linear group dispersion test a few days before  the bullets of 158.0 - 158.5 gr demonstrated linear dispersion from 100 to 300 yards.  Also after the test explained here another linear group expansion test was done at 100, 200 and 300 yards again using the mixed weight “lot” of 158.0 - 158.5 gr bullets.  The results also demonstrated linear group dispersion.  Those are shown in the RPM Threshold thread.  If we look at the CBA match results for Heavy Rifle in the 2015 Nationals we find the moa average for the 9 shooters for two 10 shot groups at 200 yards was 1.373.  Looking at the graph below we find the moa average for six 10 shot groups at 300 yards to be 1.2.  Test after test I have done, especially at 200 and 300 yards demonstrates conclusively the visual and weight sorting are indeed beneficial to accuracy.  Larry, we need explanations of what you did, how you did it, and a look at the groups-or at least the group sizes. Otherwise what you'r giving us is opinions. That's fine, but don't confuse opinion with proof or even suggestion. LMG