theory is not reality- there's VOLUMES been written on the best loads by the likes of zediker, etc- why not take advantage of his research and eliminate the guesswork on your part- consensus was the best bullet was 168hpbt, and it is a 1/12 twist- which, theoretically, should allow you to shoot up to 180s using greenhills formula- however, if you should venture above 170 , you will have to put up with accelerated wear and possibly bent/broken op-rods; therefore use zediker's formulations and stick to 168s- the reason why you find 150s is that it's the old 06 garand load and they didn't want to change bullet weights- i've got 4 of them and they all shoot better with 165-168 grain bullets