_The American Musket Nipple._—The American musket nipple has a thin edge and a wide opening at the top, so as to allow the flame to readily enter, the thin edge enabling the cap to be very readily exploded, even with the blow from a weak mainspring. In this form of nipple the detonating powder is ignited at the edge, and being forced to enter the wide opening, is compelled to pass down the vent to the powder. If there be any little dirt or obstruction, it is generally forced along with the fire, and the ignition of the powder is certain, and miss-fires are few. When nipples are made with the small opening of the vent at the bottom, coarse-grain gunpowder can be used, as it is not necessary that the grains need to be admitted to the nipple. This is the case as regards military arms fitted with nipples. The powder is too coarse to be received in the nipple when freed from the cartridge and placed uncovered in the gun breech. It has been claimed by some that gunpowder can be glazed too smooth to readily take fire, and this is a source of miss-fires. Also that the flame from the detonating powder will form a mass of condensed air around itself, preventing contact with the powder until the heat is expended. This was especially thought to be the fact when there was a volume of air between the powder and the end of the nipple. These two theories are presented for what they may be worth. _Nipples used in Sporting Guns._—Of nipples used in sporting guns there may be found the broad top, the countersunk top, the taper bored, the countersunk taper, the reverse taper, double reversed, etc., etc. They are generally put up with the screw portion made in assorted sizes. The threads also vary, being as coarse as 26 to the inch, and as fine as 32 threads per inch.