An original, old recipe from another site:
This section is from the book "The Workshop Companion", by John Phin, which is available from Amazon.
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.
Materials For Browning Mixture
Spirits of wine, 1 1/2 oz.; tincture of steel, l 1/2 oz.; corrosive sublimate, l 1/2 oz.; sweet spirits of nitre, l 1/2 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 brown, 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 barrels.
Varnish For Browned Iron
Shellac, 1 oz.; dragon's blood, 3-16ths of an oz.; alcohol, 1 quart.
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.
Ted