I know for a fact, if you shoot that Berger 90gr. VLD, you need a 6.5" twist. The groups that this bullet will shoot at 600 yds. are amazing. Ten years ago, I would have told you that a .223 did not have enough steam to shoot at that distance. If you are determined to shoot a heavy bullet in .223, I wouldn't mess around with those 69-70gr. bullets.

That 90gr. cartridge will not fit in the mag. So, if you are determined to go with a bullet that is magazine friendly, you have to go with the shorter, lighter bullets.