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Old June 29, 2013, 04:00 PM   #5
IDT
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Join Date: November 6, 2011
Posts: 48
Quote:
Did you COAL grow?
Not exactly sure what you mean here... I trim all of my cases before I size & de-prim/prime - a process that changes, slightly, the case length. The COAL is from the tip of the bullet to the bottom of the case.

Also - My results are in from my chrony shoot: (only shot 6 rounds per batch as the sky was about to open up and **** on me again)

Batch 1:
55gr HPFT
C.O.A.L. 2.222
25.3grs of AR-COMP Powder
CCI 400 Primers
16" RECCE Barrel in 5.56 with a 1:8 twist (Suppressed)

Shot 1 - 3039ft/s
Shot 2 - 3028ft/s
Shot 3 - 3027ft/s
Shot 4 - 2995ft/s
Shot 5 - 3028ft/s
Shot 6 - 2984ft/s

Average ft/s on Batch 1 = 3016 ft/s

Batch 2 = same except 25.5 grains of AR-COMP

Shot 1 - 3001ft/s
Shot 2 - 3004ft/s
Shot 3 - 3033ft/s
Shot 4 - 3049ft/s
Shot 5 - 3059ft/s
Shot 6 - 3091ft/s

Average ft/s on Batch 2 = 3039 ft/s

I had doubts about using AR-COMP on the lighter bullets, but it looks like I'm good to go. I can maintain an excess 3,000 ft/s from a 16" barrel (Suppressed) with the lighter 55 grain rounds - and that is frigging awesome for the longer distance shooting.
The primers are seated perfectly. There is zero issue there at all.
None of the cases appear to be deformed, or neck split or otherwise out of shape. I'll be putting them on the micrometer in a few and measuring the before and after trim length for the cases. It will be interesting to see if they grew. This is a 5.56 barrel...so I'm not sure what to expect there. But visually, they look great.

EDIT: - Just measured the spent brass. The original trim length was 1.746" What I didn't expect was to get a shorter case length... They measure out now at 1.743". Obviously this could be accounted for in 2 different ways of measuring the brass, and I can assume to say there was zero change in the length. However I fully expected to see SOME growth... What gives?

Last edited by IDT; June 29, 2013 at 05:47 PM.
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