450 Bushmaster
100 yards 5 shots 250 grain Hornady FTX 35.4 gr LilGun
100 yards 5 shots 225 grain Hornady FTX 36 gr LilGun
...also a decent bruise on my right shoulder. 40 rounds of .223 in an afternoon is a good start. 40 rounds of Bushy is- enough.
Also confirmed that my rifle cycles 100% with AR Stoner 5 rd mag. Not so much with std .223 mags