BROWNING, CASEHARDENING, ETC. 231 



only necessary to make the part which appears outside the 

 stock of solid metal, and let it into a socket cut in the wood. 



PERCUSSION ING. 



The adaptation of the locks to the stock and to the nipples 

 or other parts used in the firing of the gun is called " per- 

 cussioning," and this duty is performed by a special workman 

 in all large gun. manufactories. It is highly important, because 

 upon the proper strength of the spring and upon the correct 

 striking of the hammer or needle upon the cap or other 

 detonating substance depends the certainty of avoiding a 

 miss-fire. 



BROWNING, CASEHARDENING, ETC. 



The barrels are made up and proved, as well as finally 

 bored, before the last finishing-touch is put to them. This 

 consists in imparting to them an artificial oxidization by 

 means of acid, which forms a coat on the surface that resists 

 the oxygen of the air to a greater extent than the bare metal 

 will do, and the plan is therefore generally adopted, though 

 some sportsmen prefer the plain metal. If the latter case, 

 it must be rubbed occasionally to keep it bright, and in 

 course of time the thickness will be reduced, though, with 

 moderate care, this ought not to be appreciable during 

 the time in which the internal surface will continue good. 

 The following is the usual recipe for staining twisted 

 barrels : 



Take of Tincture of sesquichloride of iron, ^ oz. 

 Corrosive sublimate, 1 dr. 

 Sulphate of copper, ^ dr. 

 Nitric acid, 1 dr. to 1 dr. 

 Spirit of wine, 6 drs. 

 Water, 8 oz. 



Dissolve the corrosive sublimate in the spirit of wine, then 

 add the solution to the other ingredients, and let the whole 

 stand for a month or six weeks, when it will be fit for use. 

 The barrels are first cleaned carefully with lime, and this 

 being removed, the browning mixture is laid on with a sponge 



