I tried Leupold quick release mounts on an Encore 375 H&H Magnum and they shot loose. I would personally not have confidence that they would stay in place under a muzzel loader's recoil.
There are Encore bases/rings called Quick Sites which I got from Natchez that allow one to mount a scope and still use the iron sites. I have them on an Encore 270 Win. and a 30/06 barrel and like them. I think it's nice to have the iron site option in case there is a scope malfunction or for close targets. Not too long ago, the iron site option on my 30/06 came in handy when a ground hog was heading for his hole under my porch at high speed. I blasted him on the run from about 20 feet away; try that with a scope.