I did almost the same thing, I wanted a straightwall cartridge bolt action for Ohio this was before the 350 was out and i wanted to be able to use factory ammo.
I had a rifle i had built a few years back in 22-250 that the barrel was shot out, it was a Stiller Predator action in a McMillan
rem hunter stock I really liked that setup.
So I ordered a Pacnor 20 twist 22" barrel in the same contour to fit the McMillan
and had a local smith chamber it for the 450 Bushmaster using a bugnut from bugholes.
It has HS DBM bottom metal i had to play around with the mags to get it to feed good, I'm shooting the 200gr Barnes xpb for the 460 at 2700+ fps for a little over a inch at 100 yards i havent killed a deer with it yet but our season isnt over.