Abstract: A nipple for a muzzle-loading firearm includes a generally cylindrical main body with a forward end of smaller diameter projecting forwardly and a rearward end of smaller diameter projecting rearwardly from the main body. An ignition bore extends completely through the nipple along the longitudinal axis thereof. The rearward end includes a tapered exterior surface with a forward tapered portion and a rearward tapered portion having different slopes. An annular groove is formed in the forward tapered portion slightly forward of the rearward tapered portion, and the rearward tapered portion preferably has a steeper slope than the forward tapered portion. Each tapered surface of the rearward end tapers to a smaller diameter from the main body rearwardly.