6" groups now....different ammo could get you 2" groups. Yes...it is possible. However....for sure clean your barrel before you try any new ammo. Don't switch back 'n fourth with ammo without first cleaning the barrel. As a hand loader it's a proven fact that when you shoot the same bullet with different powders, you MUST clean the barrel before switching to the new powder or the group will not be a "true group.

Also, and I'm sure you have done this, but do a copper cleaning as well. It won't take much to copper up the 300 WSM at the speeds those bullets are being pushed at.

FWIW

Dave