To Prevent Gun Barrels from Rusting.—Heat the barrel to about the temperature of boiling water, no higher, and then cover it with a good coating of copal varnish. Let it stand at same temperature about half an hour, then rub off the varnish while still hot with a soft cloth. In this process the varnish will enter the pores of the metal sufficiently to prevent rusting, but will not show on the surface after having been carefully rubbed off as directed. A polished surface like that of a finished gun barrel, is not much liable to rust, and, indeed, seldom begins to rust, the rust starting in the pores of the metal and finally working outward. This being the case it will readily be seen that sheltering the pores by filling them with some kind of substance impervious to moisture cannot do otherwise than act as a splendid preventive.
Protection from Rust.—It sometimes happens that finished up articles in steel or iron must be laid away for a considerable length of time, in which case it is desirable to employ some means for protecting them from the effects of rust. One of the most common things is to either grease them or wrap them in a greasy rag. This may answer in many cases, but it is not nearly so good as to paint them over with a mixture of white lead and tallow in equal parts, the white lead to be such as has been ground in oil for the painter’s use. In this simple mixture will be found an effectual protection; and as the tallow will prevent drying, it may be entirely removed at pleasure by rubbing with a little kerosene or turpentine.
Where it is desirable to protect an article that must be handled a great deal, as gun-barrels on sale in a store, for instance, a very good plan is to heat the article sufficiently hot to readily melt beeswax brought in contact with it, then rub it thoroughly with the wax. Let it stand until the wax is about ready to harden, then rub off with a coarse woolen cloth. The wax remaining on the metal will not show, but there will be enough left to protect it from rust.
CHAPTER XVI.
ON WORK ON GUN BARRELS.
Boring Gun Barrels.—The tool used for this purpose consists of a rod a little longer than the barrel to be bored, with a cutter head at one end. This cutter is about one-half or three-quarters of an inch long, and of a diameter a little larger than the bore that is to be enlarged. It can be made to be pulled through the barrel or to be pushed through when cutting. In the armories where many guns of the same calibre are made, a portion of the shank, next to the cutter, is made of the bore of the barrel, and the cutter made of the size the bore is to be enlarged. The portion that fills the bore acts as a guide, so that the cutter is forced to follow after it, and the enlarged bore is in the same line as the boring previously made. The cutting edges of the tool are, of course, next to the enlarged portion. As the tool is pulled through the barrel, the cuttings are left behind it as it advances; oil is to be supplied while cutting, and care must be exercised not to let it get clogged with cuttings, as a tearing of the surface of the barrel would be the result.
When the tool is made to be pushed through while cutting, the cutting edges of the tool is on the end, and it operates like a reamer. This cutting end should be bevelled off so as to follow the bore to be enlarged.
How to make Cutters for Boring.—One way to make these cutters is like a many-fluted reamer, with five, seven, or more cutters. The odd numbers will operate better than even ones. If made with too many cutting edges, there will not be clearance enough for the chips, and clogging will be the result. Then again, the cutters must not be too long, or there will be too much friction, and the barrel will become very hot in working. Also, if the friction is too great, the barrel may be bent and sprung in consequence.
One form of cutter is made like the cherry to make an elongated bullet, or like the cherry of a Minie bullet. They may also be made in form of an egg. A common twist drill welded to a steel rod has been used for small bores. A small fluted reamer welded to a rod will do where the enlarging is quite small. When the tool is to be pulled through the cutter may be made like a short twist drill not over an inch long, with the cutting edges next the rod, and not on the end, as these drills are generally made.
Quick-Boring Gun Barrels.—The way to bore gun barrels by hand is this: Make a steel rod with a square bit about six or eight inches long on one end, and a little less in diagonal diameter than the bore of the barrel. The whole rod should be a little longer, say a foot or so, than the barrel to be bored. Harden and temper the bit end. See that it is true and perfectly straight when ground. The grinding should be done by drawing the bit across the face of the grindstone, and this will leave the sides of the bit a little hollowing, and the edges quite sharp. Pack up one side with a thin strip of soft pine until it will just enter the breech end of the barrel. By means of a strong bit stock, or a handle affixed like an auger, turn it around, at the same time forcing it toward the muzzle, until it has cut its way through the entire length of the barrel. While the cutting is going on keep the interior of the barrel plentifully supplied with good oil. Now, as the bit will be a very little smaller than the bore of the barrel, remove it and take off the little strip of wood and place between it and the bit a strip of writing paper of the length and width of the side of the bit where the wood was placed; then insert the bit again at the breech and bore through to the muzzle. Repeat the operation again by inserting a second slip of paper, and so proceed, using plenty of oil, until the bore or calibre of the barrel is sufficiently enlarged.