The A-bolt ll has 3 aluminum sleeves that run the length of the bolt and line up with the 3 locking lugs when being inserted into the receiver. The original A-Bolt didn't have these sleeves. These sleeves are supposed to prevent the bolt from binding and make the action a little smoother to operate. I believe the triggers are different too but don't quote me on that one. But from what I can remember is that the A-Bolt trigger wasn't adjustable while the A-Bolt ll can be adjusted by a gunsmith.