http://home.comcast.net/~gocartmozart/mk262.jpgThe ammo loaded with the 77 grain Nosler OTM is from the original ar15.com special group purchase. The rounds loaded with the Sierra 77 grain MATCH HP are Black Hills 2nds purchased from Cabela's.
Rounds were chronographed using an Oehler 35-P chronograph. Muzzle velocities were calculated from instrumental velocities using Oehler's Ballistic Explorer software. All strings of fire consisted of 10 rounds.
Nosler
Sierra 2ndsColt 20" A2 1:7" twist2867 fps
2806 fpsColt 16.1" M4 1:9" twist2770 fps
2710 fpsColt 14.5" M4 1:7" twist2630 fps
2628 fpsFor additional comparison I have chronogrpahed 6 different lots of 77 grain Federal Gold Medal ammo. The combined average muzzle velocity of all six lots was 2577 fps when fired from the same Colt 20" A2 barrel.