Muzzleloader systems include a pre-packaged propellant charge and primer for providing efficient loading and unloading of the muzzleloader. The muzzleloader accepts in the breech end the propellant containment vessel that abuts against a constriction portion with a reduced diameter portion. The propellant containment vessel having an end portion with a tapered surface that conforms to the constriction portion surface. A projectile is inserted in the muzzle end and seats against the constriction portion. The propellant containment vessel may be received in a removable breech plug. The constriction portion may be part of the breech plug or a separate component secured in the barrel by way of the breech plug. The containment vessel further comprises a primer mechanism that may be integrated into the proximal end of the containment vessel.