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OK Gents...I couldn't take waiting for the additional springs and buffer to come in on Tuesday and I really wanted to get my oldest behind his deer rifle before our big hunting trip next weekend. So here's what I tried today:
For the 8":
I loaded up some 1680, 10.2 grains w/ Hornady 225 Match, and changed out the buffer to a 6.3oz heavy buffer and a lighter weight Colt carbine spring. This was all inside a Rock River pistol lower with their 2 stage match trigger.
10 shot average velocity was 962 with only a standard deviation of 6. All rounds ejected and cycled. I got a little blowback (already using a PRI handle) and increased ejection port noise (less than with the H buffer and Colt spring--cycles hard; more than the Rock River heavy weight spring with the 6.3oz buffer--cycles very soft). When I switched over to a lighter buffer (H) with heavier buffer spring, the same round would eject, but wouldn't completely strip the next round. I still got some crap in the face, but it was less than the previous combination. Ejection port noise was a little less.
Then I tried N110, 8.9 grains w/ Hornady 225's, and the H bufffer with the lighter Colt carbine spring. Average velocity was 1063. None of the rounds fully ejected and it didn't cycle, BUT....the ejection port noise was a lot less with less blowback.
The way ahead....I see a few options here. First, I can find a slightly faster powder than 1680 that still generates a lot of gas. Secondly, I'll try adding the BCG weights to increase the moment of inertia and lock time while using a lighter spring and H buffer. Third, install a better buffer tube. I can feel machining marks inside the Rock River and the guys at Noveske specifically mentioned that issue causing greater friction and malfunctions. Lastly, I can pull off the gas block and install an adjustable block.
NOW FOR THE NOVESKE...
I loaded up the following loads, all with hornady 225's.
10.6 grains, 1092 fps 10 shot average, great accuracy, all cycled
10.5 grains, 1103 fps 10 shot average (better burn rate maybe??), great accuracy and all cycled
10.2 grains, 1066 fps 10 shot average, great accuracy--1 MOA side to side--ALL CYCLED
Then I switched over to 240 SMKs with 10.6 grains of 1680. 1043 fps 10 shot average. All cycled and ejected and it sounded sweet...even sweeter when I saw the 3/4" group in the spotting scope.
These were shot with the same RRA H buffer and carbine spring as last week...WTH! I'm not sure what made the difference. Since my last trip to the range, I scrubbed the whole thing with Kroil and made sure to calibrate the RCBS charge master before changing each load. Perhaps it just needed a good breaking in.
More to come...
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