_Barrel._—The iron or steel tube of the gun through which the charge passes in the act of firing. _Barrel-loop._—A metallic loop under the barrel, through which a small bolt passes to hold the barrel into the stock. _Bents._—The notches in the tumbler of a gun-lock. _Black-Walnut._—A tree, native to North America, whose wood is extensively used in the manufacture of fine gun stocks; the _Juglans nigra_ of botanists. _Binocular Vision._—Seeing with two eyes. _Bolt._—The part which, in a breech-loader, passes into the lump of the barrel and holds it into the action when the gun is closed. _Bore._—The interior of the barrel along which the charge passes. Bores are made of the following forms: True cylinders; cylinders enlarged at the breech; cylinders enlarged or freed at the muzzle; tapered to narrow at the muzzle; narrowed to close at the muzzle; cylindrical, with ring cut out near muzzle; narrowing the muzzle with depth cut out, modified, etc. Bores are also made elliptical, hexagonal, polygonal, etc. _Brazing._—Soldering iron with brass or copper as a solder. _Breech._—In earlier days all that portion of the gun back of the lock was considered _the_ breech, but now a gun is regarded as having two breeches: the breech of the barrel, the place where the cartridge is inserted, as in the case of the breech-loaders, and the breech of the stock, being that part which comes against the shoulder. _Breech-bolt._—A small iron bar used in some make of guns to assist in holding the barrel secure to the action. _Bridle._—That piece in the lock connected with the tumbler as a kind of cap. _Browning._—A rust produced on the surface of gun-barrels by means of acids. _Bump._—The corner of the stock at the top of the heel-plate. _Burnisher._—A piece of smooth and hardened steel used in polishing the surface of metals. _Calibre._—The diametrical measurement of the bore of a gun barrel. Breech loaders are made of 10, 12, 14, 16 and 20 calibre. Muzzle loader of every variety of measurement. _Cap._—The metal covering placed on the end of a pistol handle. Also the small cup-like contrivance put on the nipple upon which the hammer strikes to fire the gun. _Carbine._—A short form of rifle; so made to be easily carried by persons who used them mounted on horses. _Cartridges._—The ammunition for a gun, contained in metal or paper cases. They are sized to regular numbers, as gauge 10 or 12, etc., and are of two kinds, central-fire and rim-fire. _Case-hardening._—A hardened, steel-like exterior given to iron by heating it in connection with animal charcoal, and then plunging while hot in cold water. _Central-fire._—Setting off the cartridge by striking it in the centre, where the fulminate is placed.