08-19-2021, 03:32 AM
Okay guys here's some more data. This time was just single shots and using Hornady 6.5 Grendel virgin formed brass instead of the Starline that I normally used. I have found Hornady brass to produce 15-20 fps more velocity than Starline, but I have found Starline to hold pressures better than Hornady in terms of brass head holding up (rabbit trail over lol).
This is in my 18" Proof Research barrel w/ rifle +1 gas system, custom 6mm silencer and SA gas block tuned for 108gr Hornady 108gr Match ammo. 70gr Varmageddon is seated at 2.150" (0.050" jump).
IMR 4198: spread was around 1" ish.
24.3 - 2934 fps Did not lock bolt back, but ejected case.
24.6 - 2949 fps Did not lock bolt back, but ejected case. Slight ejector swipe.
24.9 - 2987 fps Did not lock bolt back, but ejected case. Slight ejector swipe.
25.2 - 3003 fps Did not lock bolt back, but ejected case. Slight ejector swipe.
25.5 - 3102 fps Did not lock bolt back, but ejected case. Ejector and extractor swipe.
Conclusion: IMR 4198 is too fast of a powder.
MP 405 (N133 equivalent): spread was about 1"
27.5 - 2861 fps Function normally.
27.8 - 2897 fps Function normally.
28.1 - 2917 fps Function normally. Slight ejector smear (anomaly?)
28.4 - 2962 fps Function normally.
28.7 - 2978 fps Function normally.
29.0C - 3013 fps Did not lock bolt back, but ejected case (anomaly?)
Conclusion: Will test top end for groups, maybe take it a step further, but compression might be an issue.
This is in my 18" Proof Research barrel w/ rifle +1 gas system, custom 6mm silencer and SA gas block tuned for 108gr Hornady 108gr Match ammo. 70gr Varmageddon is seated at 2.150" (0.050" jump).
IMR 4198: spread was around 1" ish.
24.3 - 2934 fps Did not lock bolt back, but ejected case.
24.6 - 2949 fps Did not lock bolt back, but ejected case. Slight ejector swipe.
24.9 - 2987 fps Did not lock bolt back, but ejected case. Slight ejector swipe.
25.2 - 3003 fps Did not lock bolt back, but ejected case. Slight ejector swipe.
25.5 - 3102 fps Did not lock bolt back, but ejected case. Ejector and extractor swipe.
Conclusion: IMR 4198 is too fast of a powder.
MP 405 (N133 equivalent): spread was about 1"
27.5 - 2861 fps Function normally.
27.8 - 2897 fps Function normally.
28.1 - 2917 fps Function normally. Slight ejector smear (anomaly?)
28.4 - 2962 fps Function normally.
28.7 - 2978 fps Function normally.
29.0C - 3013 fps Did not lock bolt back, but ejected case (anomaly?)
Conclusion: Will test top end for groups, maybe take it a step further, but compression might be an issue.
The moment you've got it figured, you're wrong.