Just thought this may be interesting to everyone.  Today I spent a few hours out at the rifle range and chronographed some ammo.  I tested the following out of both my RRA 16 inch mforgery and then out of my Bushmaster 20 inch Hbar.

I tested the Remington 55 FMJ, the Federal XM 193, the Winchester Q3131 and a couple of hand loads that I had lying around for comparison.  everything functioned flawlessly and air temp was around 28 degrees F.

I used my Competetive Edge Dynamics chronograph and downloaded the velocities into an Excel spreadsheet for the statistical analysis. Th F before a velocity indicated a potential flier.

It looks like the 2 inches of barrel makes between 150 and 200 FPS difference and the XM 193 is significantly hotter than the Q3131, although I was always under the impression that the two loads were comparable.

Also the XM193 was WAY more consistent in velocity shot to shot than any other load that I tested.  As soon as it warms up 40 degrees or so, I plan to do the same analysis and see how much of a difference temperature makes.  

Ok, so I am an ammo geek, but it IS pretty cool to be able to have an understanding of exactly what you are shooting!!!  

Remington 55 g FMJ RRA 16 inch barrel

GROUP #1 1   2       3  4   ƒ 5
Velocity: 2887 2899 2878 2875 2808 Pwr Fctr High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: 17.6 29.6 8.6 5.6 -61.4 502 2899 2808 91 2869.4 35.4 ±44.0

Remington 55 g FMJ Bushmaster 20 inch barrel

GROUP #2 1 2      3            4   ƒ 5
Velocity: 3031 3017 3028 3032 3072 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: -5 -19 -8 -4 36 531 3072 3017 55 3036 20.8 ±26.0

Federal XM193 RRA 16 inch barrel

GROUP #3 1  2       3 ƒ 4     5
Velocity: 3038 3039 3044 3053 3035 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: -3.8 -2.8 2.2 11.2 -6.8 532 3053 3035 18 3041.8 7 ±9.0

Federal XM193 Bushmaster 20 inch barrel

GROUP #4 ƒ 1 2     3         4     5
Velocity: 3218 3241 3247 3243 3237 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: -19.2 3.8 9.8 5.8 -0.2 567 3247 3218 29 3237.2 11.2 ±14.0

Winchester Q3131 RRA 16 inch barell

GROUP #5 1   2       3  4       5
Velocity: 2798 2824 2811 2820 2792 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: -11 15 2 11 -17 455 2824 2792 32 2809 13.6 ±17.0

Winchester Q3131 Bushmater 20 inch barell
GROUP #6 1   2       3  4       5
Velocity: 2981 2981 2991 2968 2973 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: 2.2 2.2 12.2 -10.8 -5.8 483 2991 2968 23 2978.8 8.6 ±11.0

Handload 55 g FMJ 26.1 g W748 RRA 16 inch Barrel
GROUP #7 1   2       3  4        5
Velocity: 2740 2698 2723 2749 2728 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: 12.4 -29.6 -4.6 21.4 0.4 442 2749 2698 51 2727.6 19.4 ±24.0

Handload 55 g FMJ 26.1 g W748 Bushmaster 20 inch Barrel
GROUP #8 1   2       3   4       5
Velocity: 2844 2906 2887 2850 2872 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: -27.8 34.2 15.2 -21.8 0.2 503 2906 2844 62 2871.8 25.6 ±32.0

Handload 55 g FMJ 27.2 g W748 RRA 16 inch Barrel
GROUP #9 1   2    ƒ 3          4      5
Velocity: 2856 2856 2897 2864 2837 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: -6 -6 35 2 -25 464 2897 2837 60 2862 21.8 ±27.0

Handload 55 g FMJ 27.2 g W748 Bushmaster 20 inch Barrel
GROUP #10 1 2      3   ƒ 4    5
Velocity: 2966 2992 2979 3031 2983 High: Low: E.S.: Ave.: S.D.: 95%:
Ave. Dev.: -24.2 1.8 -11.2 40.8 -7.2 484 3031 2966 65 2990.2 24.6 ±31.0