Ive got a 'Buck' 12ga. barrel on my old birdgun frame. It is a visious kicking beast with factory Foster type loads, but plenty accurate for 50-60yd deer. It also shoots birdshot above the sights about right at 25-30 so I think it is usable as a combination barrel.
I wouldnt have any reservations about a 357 or 44Mag, in fact the old Shikari 44M was basically the same frame IIRC (had one and should have kept it),
BTW GREAT buy!