Some data points and observations to share:
The Berger 80.5's using 26.9 -27.0 grains of CFE223 appears to be safe using my PSA 20" upper. Note that its perfectly tuned using a SA adjustable gas block. The top, single row of 10 is new, Starline brass loaded at 26.6gr just to establish a visual baseline. The bottom two rows were loaded at 27.0 grins of CFE223 using shit, once-fired Federal factory brass to ensure a worse-case visual result:
View attachment 7588916
Finally got my buddy to show up with his new, fancy 24" 1-7.5 twist Rainer barrel to do some comparisons out of two different guns. Using his gun, with him shooting, I was able to confirm the following:
- The 80.5 Bergers at 26.6 gr of CFR223 are the most consistently accurate load tested to-date across two gas guns.
- The 85.5 Bergers at 26.4 or 26.6 produce almost 3x the group size vs. the 80.5's.
- The 88 ELDM suck in both rifles with groups slightly worse than the Berger 85.5's. Also produced some failure to feed due to what I'm assuming is the ballistic tip.
The groups on the left were shot using the Rainer (after zero) and groups on the right using my PSA while zeroing. Range was just under a 100 yards:
View attachment 7588922
Nothing to write home to mom about but 5 out of 10 shots using the 80.5' sat 27.0 gr shows some real promise (lower right group). 5 of the 10 can be covered with a dime. Only loaded up 10 just for this quick test. Going out again this week (alone, no distractions, no kids, and shoot off a real bench instead of a card table!) to test against 26.6 vs 27.0 grains. I'll also chrono.