I'm just a hunter who shoots off a bench for load development. With a Kimber Montana in .300WSM (i.e. hard kicking, light rifle), I place the gun so the recoil lug lines up with the front rest, firmly pull the butt straight back into my shoulder, adjust the gun so the reticle sits just above the target dot, and then squeeze the bag with my left hand for the final alignment. 30 round is about all I can shoot in one session before my shoulder says "enough."
I've tried pulling down on the forearm, placing my hand over the scope, and a few other techniques recommended by expert shooters for light rifles, and the groups have always opened up compared to the above method.
