The 722 was a 244 when I picked it up. When I rebarreled it it had a 1 in 10" twist, so I guess that you could call it a 6MM Remington. I used two different powders RL19 and IMR 4350. I believe that the barrel steel was soft. Rocky Mt Rifle works uses a cut rifling method to rifle a barrel. The rifle was never shot rapid fire. It was a primarily a varmint rifle. Never the less the barrel was heat checked over a third of the way up from the chamber. The load that I used mostly was a Sierra 85-grain Bt Hp over a powder charge of 45.5-grains of IMR 4350.