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9/19/2017 7:27:10 PM
Posted: 2/1/2006 4:07:05 PM EDT
I had the good fortune of being able to shoot today, and used the chance to collect some Chrony data.

I shoot the following rounds from a 16” (gasp) Model 1 upper. It was a blistering 40°F. Not bad for February 1. All strings were five shot.

Radway Green M855

High 2986
Low 2921
Extreme Spread 64.87
Standard deviation 27.20
Average 2951

ADCO M855

High 2881
Low 2802
Extreme Spread 79.41
Standard deviation 32.49
Average 2852

Brunell 62grain Hollow Point

High 2922
Low 2875
Extreme Spread 47.23
Standard deviation 26.85
Average 2906

Wolf 62 grain FMJBT This is the older and obviously slower stuff

High 2793
Low 2690
Extreme Spread 102.4
Standard Deviation 41.94
Average 2750

M855 Clone using Reloader 7 @ 21.5 grains and ss109 62 grain bullets

High 2806
Low 2723
Extreme Spread 83.34
Standard Deviation 30.61
Average 2770

From they way the spent cases ejected I would have guesses this was a much slower load than it turned out to be. The empty cases literally fell at my feet. According to my manual (which is quiet old) this is the max load. But I think I will bump the charge up a grain or a grain and a half to see if I can get to 2850FPS.


The following round I shot from a 24” bull barrel. I was not going for groups but it did look like they had potential.

Black Hills 68 grain match boat tail hollow point.

High 2832
Low 2743
Extreme Spread 89.24
Standard Deviation 39.94
Average 2779


Thanks for looking thebrain
Link Posted: 2/1/2006 4:25:24 PM EDT
[Last Edit: 2/1/2006 4:27:17 PM EDT by Samuel_Hoggson]

Originally Posted By thebrain:
M855 Clone using Reloader 7 @ 21.5 grains and ss109 62 grain bullets

High 2806
Low 2723
Extreme Spread 83.34
Standard Deviation 30.61
Average 2770

From they way the spent cases ejected I would have guesses this was a much slower load than it turned out to be. The empty cases literally fell at my feet. According to my manual (which is quiet old) this is the max load. But I think I will bump the charge up a grain or a grain and a half to see if I can get to 2850FPS.





Not at all surprising. Port pressure and dwell determine bolt carrier movement parameters. RL7 is a bit fast on the burn scale - faster even than IMR 3031. I would guess that something slower like 748 (or even H335) would give more forceful ejection (higher port pressure).

Thanks for posting the data!

Sam

ETA: Pls, pls don't assume that b/c ejection is weak you must be below maximum pressure. To take the analogy further, you would KB the gun before you could get the gun to cycle even once using Alliant Bullseye.
Link Posted: 2/1/2006 4:41:34 PM EDT
Point taken

Thanks for the insight.
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