When chambering barrels for breech-loaders, the utmost care should be observed to make the chamber exactly concentric with the bore, and have it smooth and well finished. Do not trust to a drill or a flat reamer; neither will a half-round or a common fluted reamer answer the purpose. Take, for instance, a bore for a thirty-eight cartridge. Fig. 38 shows the tool for chambering, and Fig. 39 the tool for recessing for the head of the cartridge. The diameter of the tool for chambering is thirteen sixty-fourths. The tool for recessing for the head is seven-sixteenths. The body of the cutting portion is about seven-eighths or an inch long. An extension is formed beyond the cutting part which must exactly fill the bore of the barrel and serves as a guide to insure the cutting part making the chamber in proper relation to the bore. [Illustration: FIGURE 38.] The neck or recess in front of the cutting part is for a three-fold purpose; it forms a receptacle for the chips or cuttings, which otherwise would clog the tool as soon as the teeth were filled, and would probably result in a rough surface by being forced between the wall of the chamber and the tool back of the teeth; it also serves to produce a better shaped tooth, which is done with a fine cut three-square file, and finally by the teeth being made below the surface of the extension a square cut is produced with no feather edge where the chamber terminates. [Illustration: FIGURE 39.] The cutting teeth of the chambering tool are made so as to produce a bevel at the end of the chamber, and by this means avoid shaving the ball, as would be the case if it passed over a sharp angle. The recessing tool is made square on the cutting end. [Illustration: FIGURE 40.]