Abstract: A nipple for use in firearms employing percussion caps. The nipple includes an elongate body adapted at one end to receive a percussion cap, and adapted at its opposite end threadably to engage the ignition chamber housing of a firearm. A passage extending axially through the nipple includes a cylindrical primary section communicating with the cap-receiving end of the nipple, and a cylindrical constriction section communicating with the opposite end of the nipple body. These two sections intersect planar end faces of the nipple body substantially normal thereto. A cone-shaped section interconnecting the primary and constriction sections is dimensioned to have a greater volume and a lesser axial dimension than the constriction section.