I would try the maker of my rifle first.
Danger,Do not attempt this!.
need a fair price of what it might be worth for an old richland arms 45 cal. black powder rifle with serial no. 2142
Flexible M1919A6 Cal. .30 Browning Machine Gun M3 Cal. .45 Submachine Gun M3 Trench Knife M7 Grenade Launcher M9 2.36-in Rocket Launcher M2 60-mm Mortar M1911A1 Cal. .45 Automatic Pistol Boys Cal. .55 Antitank Rifle M1 US Cal. .30 Rifle Sniper's M1903A4 US Cal. .30 Rifle
The rifle is marked .45 but they messured this from land to land inside the barrel not groove to goove. a .433 with a .18 patch seems to be the common load. 45 is just to tight for the rifle
$100-$125
50-200 USD
Follow instructions in the owner's manual.
depending on condition, $100-$150.
You need the services of a gunsmith
100-500 usd
Most ordinary modern manaufacture caplock muzzle loaders are selling for about $100-$150, depending on make/model/condition.