I shoot a Remington 700 inline 50. They don't make them anymore and they are very accurate. This one is set up for a primer, but could easily be changed to a musket cap.
REMINGTON Model 700 ML 50 Cal Muzzle Loader - Black Powder Rifles & Muzzleloader Rifles at GunBroker.com : 800125700
REMINGTON Model 700 ML 50 Cal Muzzle Loader - Black Powder Rifles & Muzzleloader Rifles at GunBroker.com : 800125700