Abstract: Provided is a cartridge for a muzzle loading firearm. The cartridge includes a cylindrical sleeve portion defining an interior passage and a forward end comprising a tapered portion. A propellant charge is disposed within the interior passage, and an end cap defines a recess into which the tapered portion extends while the end cap is installed on the tapered portion. The end cap comprises a first fastener portion that cooperates with a second, compatible fastener portion provided to a bullet. The second fastener portion is disposed adjacent to a rearward end of the bullet to establish a friction fit between the bullet and the end cap that maintains a position of the bullet on the cartridge to be loaded into the muzzle loading firearm.