The excellence of a gun depends very much upon the form and finish of the interior of the barrels, and as the owner may, if he chooses, work the inside of his gun over so as to improve it, we give a few directions.
It has been found that a perfect cylindrical tuoe is not the best form for a gun barrel. Guns shoot most closely and strongly when the bore is very slightly enlarged towards the muzzle. This enlargement is easily effected by means of very fine emery paper wrapped about a round rod and used with a little oil. The freeing may extend to about one-third of the length of the barrel, and the gun should be tested from time to time during the process, so as to get the very best results. The testing is done by firing a standard charge of powder and shot at a sheet of brown paper and noting the number of pellets that are put into a circle of given size, and also the force with which they are driven into a board. For ordinary bird guns, a 30-inch circle at forty yards, makes a good target.
One of the great difficulties which the sportsman has to contend against is the rusting of his barrels, even when protected by the best browning. The alkaline matter existing in snow and in rain, under certain conditions of the atmosphere, works through the best coatings, and reaches the iron. Varnish, as ordinarily laid on, is objectionable, as it gives a gun a " Bruniniagein " look. The best plan is the following: Heat the barrels to the temperature of boiling water (not any hotter, or you may injure them), and rub them with the best copal varnish, giving them a plentiful coating. Let them remain hot for half an hour, and then wipe them clean with a soft rag. In this way you can get enough of the varnish into the pores of the metal to act as a preservative, and, at the same time, no one would suspect that the barrels had ever been touched with varnish. We have applied boiled oil, beeswax, paraffin, and some other substances, in the same way, and obtained good results; but on the whole, we find nothing better than good copal varnish.
To obtain a handsomely browned barrel, we must not only use a first rate recipe, but we must apply a good deal of skill and no small amount of hard work. When barrels are imperfectly browned, the fault lies more frequently in defective work than in the use of a poor recipe.
The following are the directions given in the United States Ordnance Manual, and it is to be presumed that these are the directions that are followed in the government armories.
Spirits of wine, 1 1/2 oz.; tincture of steel, l 1/2 oz.; corrosive sublimate, l 1/2 oz.; sweet spirits of nitre, l1/2 oz.; blue vitriol, 1 oz.; nitric acid, 3/4 oz. To be mixed and dissolved in one quart of warm water, the mixture to be kept in glass bottles and not in earthen jugs.
Previous to commencing the operation of browning, it is necessary that the barrel or other part should be made quite bright with emery or a fine smooth file (but not burnished), after which it must be carefully cleaned from all greasiness; a small quantity of powdered lime rubbed well over every part' of the barrel, is the best for this purpose, but in the case of old work, which is very oily or greasy, or when the oil or grease has become dried or gummed on the surface, the barrels must be first washed with a strong solution of potash in warm water. After this the lime may be applied. Plugs of wood are then to be put into the muzzle of the barrel and into the vent, and the mixture applied to every part with a clean sponge or rag. The barrel is then to be exposed to the air for twenty-four hours, after which time it is to be well rubbed over with a steel scratch-card or scratch-brush, until the rust is entirely removed; the mixture may then be applied again, as before, and in a few hours the barrel will be sufficiently corroded for the operation of scratch-brushing to be repeated. The same process of scratching off the rust and applying the mixture is to be repeated twice or three times a day for four or five days, by which time the barrel will be of a very dark brown color.
"When the barrel is sufficiently l:rown, and the rust has been carefully removed from every part, about a quart of boiling water should be poured over every part of the barrel, in order that the action of the acid mixture upon the barrel may be destroyed, and the rust thereby prevented from rising again.
The barrel, when cold, should afterwards be rubbed over with linseed oil or sperm oil. It is particularly directed that the steel scratch-card or scratch-brush be used in the place of a hard hair-brush, otherwise the browning will not be durable nor have a good appearance.
If the work be handled with unclean or greasy hands, imperfectly browned places will show where the hands have touched the ban-els.
Very complete directions for browning gun-barrels may be found in a little book called "Shooting on the Wing," which may be obtained from the publishers of this volume.