Bigcountry is the one to ask about that one! He has one,and can tell you all about those big boys. Usually on most guns from 200-300 rounds.I just finish building a 243 and have got some groups as low as .330 to.890 with less than 40 rds through it.Just imagine what it might do when the barrel settles in?? But Bigcountry can tell you,im him. vangunsmith