_Preparing Nipples for Guns._—It is well for the gunsmith to test the nipples with a fine file to ascertain their hardness before inserting them in guns. If too soft, they will be returned on his hands. If there is also a liability of the gun-hammer battering the top where it strikes, which soon is so broad as to cause miss-fires. If too hard, they are liable to break short off at the square, and the screw portion left in the gun is difficult to remove. Sometimes so much so that it is necessary to unbreech the gun, remove the patent breech and heat it to soften the portion of broken nipple so that it can be drilled out. In drilling there is a risk of injury to the thread of the nipple seat. The heating necessitates labor to refinish the part and it is to be again case hardened before screwing into the barrel. If found too hard, nipples can be drawn to a better temper by holding the top portion in a pair of pliers in exposing the bottom part to the flame of an alcohol lamp. If they be too soft, enclose in a short piece of gas pipe, pack them well with bone-dust, stop close the ends of the pipe, and heat to a red, letting them remain so for fifteen or twenty minutes and then open the end of the pipe to let the contents fall into water. They can be drawn to temper to suit. They may also be heated hot, rolled in prussiate of potash or cyanide of potassium, again heated, and thrown into water. As cyanide of potassium is a deadly poison, be very careful how it is used and where it is kept. Do not breathe the flames when put on hot iron, and do not let it come in contact with sores or raw places on the hands. _Remedy for Bad Nipples._—In case guns come in to be repaired because they will “not snap a cap,” see if a weak mainspring be not one cause, and a nipple with broad top, another. For the latter evil, ream or counter sink it so as to have a thin cup like edge. See also if the cup of the hammer strikes properly on the nipple, and that it be not too much cupped by long usage in striking. In this case, the cup may be filled by drilling in and inserting a bit of iron or steel to fill it and then re-harden. _Pistol Nipples._—Pistol nipples, Colt’s for instance, have a different thread from gun nipples. The thread used in Colt’s revolver nipples is 40 to the inch. But one size is employed—nipples are sometimes provided with a thin, round washer of copper, which is put on at the shoulder where the thread terminates. This shields that part of the seat where it is placed from rust, and some claim that it acts as a sort of cushion to deaden the blow of the hammer, thus preserving the nipple from breakage.