It would probably need some minor work.
I built a .404J on a .300 RUM donor. Some work had to be done to tweak the bolt face, but that wouldn't need to be done here.
The feeding ramp had to be slightly widened for the fatter bullet to feed slick and a 450 conversion may need similar treatment.
It would be pretty close to the short .458 WM, which had gotten some good reviews.
DF
