I am planning to build a fast twist 22-250. My primary use would be paper punching/clay targets out to about 600 yards. Secondary use would be prairie dog shooting with occasional use on coyotes. I would like to use up to 75g AMAX and similar bullets. I am considering either a 1:9 or 1:8 twist. I have read that the 9 twist will give slightly better velocity than the 8 twist with the heavier bullets and better accuracy than the 8 twist with bullets in the 50-60g weight range. I have also read that the 8 twist produces better accuracy with 75g bullets and heavier. Is the choice between the two twists really that critical or is this mainly a hair-splitting excercise? If I intend to shoot the heavier bullets (75g and up), would going to the AI chamber be worthwhile? In my current 22-250, I am using mainly Winchester brass. For those who have used it in this chambering, have your found Lapua brass to offer an edge in accuracy?