I have been running a Whitely 6mmAR, which is essentially the same cartridge) in my gas gun for for about 15 years. I use 28-29gr of R15 with 105/107 gr Bergers and SMK's at 2700-2800FPS. Exceptionally accurate, and +20 reloads using necked down Lapua(6.5 Grendel) brass. My go-to rifle for 300...