+1 on loading up some 80's. i've tried my 69gr load @ 600...it aint pretty. (69gr SMK under 25gr RL15). same cases, same primers, and an 80gr SMK under 24.2 RL15 and it'll clean the target if i could do my part (just this past weekend, i cleaned my first 15 @ 600, with 8 X's)
i know one thing i struggle with BIG time is consistent head position and sight alignment. if i break position beyond turning my head to check the scope, i struggle with rebuilding my position. i coped by trying to never take the rifle out of my shoulder (if it doesnt move in my shoulder, my head almost always seems to find the same position, nose right up on the charging handle.
best bet's definately gonna be coaching. i've been picking everyone's brains that'll still listen to me. in the last year i must have gone through 4 or 5 different position changes, 3 or 4 different ways of rigging my sling, and probably 4000rounds of .22lr in my .22 upper (mostly offhand practice). speaking of which, 100yd prone practice with a .22lr has been AWESOME practice for me so far this year. those .22's are incredibly unforgiving to position problems, and you tend to know right away if you do something wrong.