The little wedge through the fore-stock hardware and barrel, plus the hook breech type of removal able barrel was kind of standard for many muzzle loaders. Although, it could be used to interchange barrels, the main reason was to aid cleaning. Black powder is dirty and nasty, but removes easily with soapy water. Remove barrel from stock. Sit breach in a bucket of hot soapy water. Stick a jag and a cloth patch down barrel, once it is bottomed out slowly pull up, the swab will act like a pump and suck some hot soapy water into the barrel through the nipple hole. Up down, flushing water in and out the nipple. Water will turn black. Change out water, finish with HOT clean water. Hot barrel will evaporate any water. Then a passs with lightly oiled patch and a wipe down.
At least thats how I was taught to clean a muzzle loader.