Mine is the WW1 era H&R small frame .44/.410 Garden Gun, originally with 2-inch chamber. John rechambered the shotgun barrel to take modern 3" .410 shells. Shotgun barrel is now 20" long with cylinder bore .425" because when I was a kid I stupidly burst the muzzle shooting .44-40 softpoint jacketed rounds in it, which didn't make it through the full choke, so last 6 inches got cut off and front sight bead remounted.
The short barrel cylinder bore .410 is far more useful in the woods, using either shot or ball and shoots skeet patterns. Game Getter ball loads in .44-40 brass with .425 soft lead ball and 6 grains of Bullseye get 1000 fps and will stay in black of a B8 repair center at 25 yards just looking down the barrel. Normal .44-40 cowboy loads with bulleted ammo shoot wild in the smoothbore barrel and won't stay on the target paper.
I found a Marlin 1894 .44-40 barrel on Numrich. John cut the threads off that, set back, made and fitted underlug and ejector. Chamber is not to SAAMI, but to old school black powder dimensions which John uses to restore 1873 Winchesters when relining. Shoots 2-inch 50 yard groups with Accurate 43-215C 215-grain soft lead .430" bullet with 6 grains of Bullseye, for 1080 fps. Same load in a 5-1/2" revolver gets 880 fps. Decent woods deer gun within 50 yards. The .44-40 single shot finished with a 19" barrel weighs 4 pounds, only 34 inches overall. Great backpack gun. My .38 Special and .45 Colt barrels were fabricated from Green Mountain 20-inch "gunsmith special" blanks. Overall very satisfied with John's work.
The .38 Special barrel shoots well with .38/44 Heavy Duty loads I use in my Colt New Service and give 1200 fps in a 20-inch rifle with 173 grain Keith bullet and 14 grains of 4227, vs. 1050 fps in the 5-inch New Service Colt. In .45 Colt 7 grains of Bullseye with 255 grain #454424 gets 1050 fps in the single shot rifle, vs..900 fps in 5-1/2" Colt revolver. All good woods loads.