Yeah I really want to use AICS mags and as long as the capacity is 3 or so I'm good. I just want reliable feeding. I'm assuming it's possible since both Savage and Ruger are now offering .450 Bush bolt guns. The other question regarding shank size, I was just thinking the large shank has a longer tenon which would provide more support for the large diameter heavy barrel. I'm thinking a varmint weight 20-22" with 0.8" or so at the muzzle.