Ahh - I see now. Pape, an American gun maker, patented or attempted to patent a screw-on choke for single barreled smoothbores in about 1855. Likely on or for a muzzleloading fowler at that time.
There is a big difference between military guns and the way they were loaded, to actually working up a fairly accurate load for as smoothbore with round balls.
Side by sides or singles, loaded with patched round balls do very well for accuracy to about 75 yards. Indeed, on our trail-walk, we have a goose target at 109yards (100meters) and with his Pennsylvania 20 bore Flint flowler, my bro has never missed that accursed target.
One other fellow in our club has only his flintlock smoothbore, yet he is never the low score on the trail shooting against rifles. He loads a .020" patched .595" ball with 85gr. 3F in a Pennsylvania fowler he built.
The bore on the gun is of course smooth and of .620". Taylor (bro) loads a .600" ball with a .020" patch - so it's snug. No rear sight, either, just a blade on the front of both guns.
I have successfully loaded for a shortened (26" tubesIIRC) breech loading 12 bore with naked balls held in the base cups from AA trap loads & powder charges up to 190gr.(7drams)
Regulation was very good as well and I was able to hit consistently, a 12" square plate hung at 100 meters, offhand, rights, then lefts, rights then left again. 4 in a row with the 7 dram charge. The light 7 1/2 or 8 pound gun kicked a bit.
Of course, with no chokes, it did not shoot shot very well and I never worked on that, however it did give slighlty better than cylinder bore patterns to 30yards with the use of shot cups.