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Re: hour glass ammo???

PostPosted: Tue Feb 13, 2018 8:03 am
by Hoot
Robert FL wrote:The unfired BB with 275 Barnes measured 1.715". I measured a new Hornady and it was 1.691"

Interesting. That 1.715 is beyond SAAMI spec. Not surprised at the length however. When I was playing with the TightNeck project, I too noticed that the cases, as you would expect, grew longer as you squeezed them down in diameter. No surprise there. Applying the total change of 1.715 to 1.694, if those hour glass cases had been trimmed to 1.695 before loading them, which is what a lot of normal cases go with, the resultant shrinkage would have left the cases at 1.674, also beyond SAAMI spec. I usually don't use brass shorter than 1.685 when the results count, but save the shorter ones down to 1.68 for foulers. Shorter ones will work as long as you strive to use cases that are all the same length in a test run. Helps tighten up the velocity SD when using a taper crimp. FWIW...