I have been playing with loads for my RPR 5.56. I bought one of these and took measurements for the 75gr ELD bullets. I came up with 2.46. I loaded some rounds to test and had no issues just didn't find the accuracy I was looking for with the powder I had on hand. I decided to give them a try again this time with a different powder, I bought a new box of bullets and measured again. This time when I measured I came up with 2.42 COAL, I measured half a dozen times and came up with the same within .002 each time. Any ideas?
Hornady OAL gauge
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It's NOT usual for a different box/lot of bullets to have a different COAL . . . or even with the more important BTO. .002 isn't going to change your ballistics enough to be noticeable, if at all.
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No, I am measured 40 thousands difference from old bullets to new. The .002 was me measuring 6 new bullets and getting the same result. I don't know how I could have measured them that far in error last time. I loaded and shot them at that length with no issues. Just trying to figure out my mistake.
.040 is a huge difference, especially for a bullet that's 75 grs. The first thing I'd do is weigh them to be sure that the bullets are actually the same bullet. Also, I'd take a close look that the shape of the bullet to be sure that they the same ELD bullet. Sometimes, though rare, manufacturers can package some of their bullets in the wrong boxes labeled for something completely different.
Assuming that the old and the new are actually the same bullet, I'd measure the bullet's base to ogive (BTO) and see how much difference there is as this is a more important spec than the COAL. If that measurement is close to that .040, then that'll likely have some effect on your accuracy and some adjustment will likely be needed (depending on the type of shooting you do).
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