I bought an H&R 45 colt Carbine at a gunshow yesterday, HX prefix, last 3 numbers engraved in the underlug of barrel match last 3 numbers on the frame. The frame interior finish and firing pin hole size look like an SB2 frame, but it has the case hardened coloring of the SB1 frames, which is it? Also will an H&R recoil pad fit inplace of the brass butt plate? My 20GA tracker II barrel locks up like it was factory fitted to this frame (pre-remington) but I don't want to shoot the shotgun with a brass butt plate. I bought a box of Winchester 250 gr. Cowboy Action rounds, shucks that is just plain fun! JamesIII