On average you can look for 900-1,200 rounds for accurate magnum barrel life! W/ the RB format I’d say 900 rounds. That ain’t much and for that reason I don’t bring a magnum to a RB match! Steve’s match is a whole different animal. In my opinion, and you can take it for what you paid, RB maximum caliber would be 6.5 mm. Sixes will beat a 6.5, 7 or .30 all day long at 600 yards. When the wind gets up and the range moves past six, K’d bar the door and a .30 will whip them. Been there and done that!