Velocity of Factory 5.56/.223 Rem ?

[J.C. Kerns]

Has anyone besides me chronographed any factory ammo in a 20" Ar-15 ? I've shot several brands and styles and never got the advertised velocities. I know a 20" barrel won't do what a 24" will, but Military specs call for M193 (55 grain) ball to run about 3200+ and the all stuff I have tried that was advertised as "military spec usually ran just over 3000 FPS in my 20" Ar.

Maybe I have a faulty chrono ?

 

[magna19]

My Windham Weaponry 20" AR15 does over 3400 with the M193 ammo. Shoots it around .75-1.0 groups at 100 yds. The several 223 Rem. stuff ive tried runs right at claimed velocity and shoots a lot tighter groups. So far all the 5.56 ammo tried is pretty hot in mine. The chamber in my gun was designed more for the 223 rem ammo. from what I have read from WW. Those numbers you mentioned would not have me think faulty chrono though its possible.

 

[scottb42]

Here is what I found in my records:

20" Colt barrel:
Federal 55gr FMJ (40 rds) = 3124 average
Hornady 55gr SP (50 rds) = 3103 average
Hornady 55gr SP (20 rds) = 3112 average
Black Hills 60gr VMAX (20 rds) = 2974 average
Black Hills 60gr VMAX (15 rds) = 2995 average

20" DPMS barrel
Hornady 55gr SP (10 rds) = 3058 average
Hornady 55gr SP (10 rds) = 3029 average

 

[turkeyrun]

I would suggest a side by side comparison with at least one other chrony, 2 or 3 would be even better.

 

[J.C. Kerns]

I think it might indeed be the chronograph that I'm using. It reads lower than expected on most of the gun/ammo combinations that I try.