this is a couple of years old, but I am currently under load development using 8208xbr. Previous barrel was a Rainer Arms match (Black Hole Weaponry) polygonal bore 1:11 heavy profile 20" with a lo-pro gas block (150 round ct.). Re-forming mandrel turned and polished to .306. Max loads as follows: IMR4895 44.5 grains 175 smk COAL 2.81 vel 2590 avg, RL-15 43.5 grains 175 smk COAL 2.81 vel 2450 avg, Varget 47 grains 155 palma coal 2.80 vel 2808 avg, IMR8208xbr 41.5 grains 175 smk COAL 2.81 vel 2550 fps. The XBR loads started at 39 grains, never had a problem with cycling the action. I have since moved to a 24" bull profile 1:10 twist, just broke in. Sentry 9 adjustable gas block turned down to barely cycle the 41.5 grain loads. Starting at 42 and going up with my next "test day". I will let you all know
