Shot some paper today with 69gr TMKs, beautiful sunny day, 70 F with 9 mph L->R winds.
First time out with a liner comp muzzle break.
Good news on dinged cases,,, no more dinged shoulders(on 55).. thanks for all the help here at PM..
Combination of stiffer flat wire buffer spring, heavier H2 buffer, polished inside of ruff extractor claw, and padding on the deflector solved it.
Here's today's results from my 20" 1:8 GM 223 barrel, with 8208 XBR, CCI BR-4 primers, COL = 2.255", cheap brass:
23.6 gr => 2805 fps ave
23.8 gr => 2827 fps ave
24.0 gr => 2890 fps ave (my choice of speed & accuracy for yotes in this AR)
24.2 gr => 2960 fps ave (WSR primer and 2.250 C0L, 5 shots, only 3 recorded fps)
Only the last load showed minimal primer flattening, all other were good.
All cycled flawlessly and no ejector marks.
I shot 10 round groups of each except for the last, will add some target pics later.
Normal caution that the top 3 loads worked for me, in this gun, and ymmv..