BTW, the "fragmentation threshold" reference is to military FMJ, not civilian SP's or JHP's, which will expand/fragment reliably at much lower velocities than 2700fps.
February 27, 2010, 02:34 AM
I have often gotten disbelief from people who don't know the M4 is shorter than our AR Carbine's and that we have a slight advantage with one that is 10% longer.
February 27, 2010, 03:33 AM
That chart is weird... M16 is 16'' right? How is it faster than the following '16''' column?
February 27, 2010, 06:08 AM
That chart is weird... M16 is 16'' right? How is it faster than the following '16''' column? The M16 uses a 20" barrel.
That chart is also very close to the difference I got between a Colt AR 20" HBAR and another Colt AR, 16" 6721. Using winchester USA 55 grain load on a slightly warm 82 Deg F day. I recorded 3263 FPS out of the 20" Colt. VS 3132 FPS out of the 16" Colt. For a difference of 131 FPS.
February 28, 2010, 12:43 AM
Holy cow! I was always under the impression that the M16 was 16''. Stupid me :p
February 28, 2010, 01:51 AM
however, if you hang around the reloading forums, or people who own chronographs, you'll find that
1) 20 different rounds from the same lot of ammo may have more than 100 fps difference between the fastest and slowest measured
2) the average speed (constant ammo) through individual barrels of the same length may vary by 100 fps due to differences in chambers, rifling, lining, etc
i mostly just work on trigger control these days
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