You and your brother just made my day. Thank you both, very much, and thank you, MVP Forum. I've been looking for nut and tenon data forever. I should visit here more often. Asking Mossberg is still a fool's errand. That said, are you going to post some of the 308 MVP data, too? I'm assuming the action will be different, I really don't know. I had heard for the longest time from various sources that the 5.56 MVP had 1.0"x20TPI threads(?) Good thing I checked here before going ahead.