There are several places from which you can order a "trade gun" or fusil. They are smooth bore early frontier style guns and usually come in shotgun ga sizes. They can be loaded with either a patched round ball or wad and shot.
Generally they are not cheap even in kit form. I have one in 24 ga, which is also 58 caliber. There is a fairly big popularity of these and most of the muzzle loader supply houses sell parts or kits. Mine is from North Star before it was taken over by North Star West. Centermark sells some, Track of the Wolf, Dixie Gun Works, etc. Jim Chambers, Tip Curtis, Rifle Shoppe, Rather than a rough kit (plank and bag of metal pieces, you may want to look for a gun that is assembled but not polished and finished, Known as "in the white" Pecatonica River, Dixon's, there's probably a few dozen. I know of guys who bought a used long rifle and had a gunsmith ream out the rifling to make a smooth bore.
Double barrel flintlocks come up for sale sometimes. Major Cha Ching!
built mine 20+ years ago. 20 gauge/.62 cal. 31" barrel. best gun i have ever owned. i have hunted and killed a truck load of stuff over the years with it. you won't be disapointed if you get one! track of the wolf has a good kit for $670.00, check them out.
Hey Guys, a stupid question, but I have never owned a flinter shotgun, and might be off on the caliber vs. bore. Can you not just overbore a 50 cal rifle, to, I think they would be 62cal. (20ga?) or 67 (12ga?)??
boring and reaming a rifle barrel into a shotgun has a few challenges. One, is that the barrel wall thickness of the breech area needs to be thick enough to withstand the pressure of the charge and then depending on how it is done, you must leave sufficient barrel wall for threads. For instance the breech plug for a TC 50 cal Hawken has 5/8 inch maximum diameter. If you bore it out to 20 ga, (62 cal) , there will be no more barrel threads to attach the breech plug. This can be overcome to an extent by not boring all the way back to the breech plug threads. However with a barrel only 15/16 (.9375) boring it out to 62 means the barrel wall at the breech is only .156. That is pretty thin for a breech wall. Taking a 50 caliber barrel out to 28 ga, (approx 55 caliber) still leaves sufficient barrel wall thickness at the breech.
I recently had a 15/16 50 caliber CVA Bobcat barrel reamed out. The retired gunsmith that did the job managed to just ream out the rifling, leaving the bore about .510. This will permit me to use a heavy patch and 495 round balls or to use a wad and shot. Circle Fly sells wads for the 50-70 Gov't which has a bore diameter of .515. I may even be able to shoot my 50-70 bullets out of the smooth bore.
Another consideration about just reaming out a bore, is that oct barrels are very front heavy and do not swing well to follow and lead flying game. I is possible to shave some weight off an octagon barrel. By turning the barrel into a round barrel from the end of the fore arm forward.