TBANSACTIONS OF SECTION G. 821 



^flFect their purpose as they are nearly smokeless, and have been successful im- 

 provements. In their early manufacture they were imperfect and irregular in 

 their force, and if heated to 80° Fahrenheit acted with great violence. Hence 

 many guns were broken by them at first, and the need has been felt of some 

 reliable instrument to measui-e the force which powders exert and its rate of de- 

 velopment. 



One of these, the Bouleng^ chronograph, indicates the velocity of a bullet 

 during its flight between two targets 60 feet apart. These are respectively con- 

 nected with suspended weights by an electric current. On the bullet piercing the 

 targets the current is broken, the weights are set free, and hence the velocity and 

 the projectile force employed are deduced. The gauze targets, however, appear 

 likely to interfere with the velocity of small shot, and to aflect the calculation for 

 them. 



The instrument known as the ' crusher gauge ' is a cylindrical nozzle having an 

 external screw to screw into any powder chamber. It is bored at one end to 

 •receive a perfectly fitting piston. On exploding powder in the chamber the piston 

 delivers an impact upon a loose copper disc placed inside the crusher gauge, of 

 which the rate of compressibility is ascertained previously. By carefully measuring 

 the thickness of the copper disc before and after the experiment, the compression 

 the disc has sufiered is observed, and the powder force is deduced. Since the 

 thickness of the barrel of a gxm from breech to muzzle should diminish proportion- 

 ally to the progressive decrement of gas pressure the lightest safe section can thus 

 he found. This instrument has been screwed at equal distances along large guns 

 for that purpose, and the principle seems capable of application to sporting guns. 

 The paper then dealt briefly with the subject of impact. 



The author exhibited a test gun of j~ of an inch calibre, designed for testing 

 the pressures exerted by difierent powders upon the barrels of guns. The upper 

 side of the baiTel is pierced with six tapped holes, into which gun-metal stop-screws 

 are screwed. On removing either of these, an instrument for measuring the pres- 

 sure may be screwed on. The stem of the piston in this instrument extends to 

 the inner surface of the barrel, and its outer extremity carries a toothed rack. 

 This engages with a pinion, the axis of which canies an index finger ranging over 

 a graduated arc. 



On firing the gun, a gas-check wad upon passing the end of the piston-rod 

 exposes it to the pressure of the gas then generated, forcing the piston upwards 

 against a spiral spring and compressing it. The compression is automatically re- 

 corded on the graduated arc in tenns of hundredths of a ton per square inch. By 

 interposing a different piston the gun becomes a crusher gauge at the same places 

 along the barrel, whereby a second test is established. 



2. Recent Improvements m the Manufacture of Rifle Barrels, 

 By Arthur Greenwood, M.Inst. G.E. 



The introduction of steel rifle-barrels some five and twenty years ago, and the 

 gradual substitution of that material in place of welded wrought iron for the barrels 

 of military rifles and arms of precision, have caused great changes in the machinery 

 •employed in their manufacture. A short description of such machinery may not be 

 without interest in this great centre of firearms industry. 



The barrels generally used for military rifles are made from mild steel rolled 

 •solid and the bore drilled out. This is necessarily a costly operation, and numerous 

 attempts have been made at hollow rolling to avoid the expense of drilling. 



To effect this barrel * blanks ' or short pieces of steel have been drilled and 

 •afterwards rolled on a mandril to the desired length, and many thousands of 

 harrels have been made on this plan. Of late years, however, the military 

 authorities have insisted upon barrels being first rolled solid to the desired form 

 And afterwards drilled. At the Royal Small Arms Factory at Enfield a system 

 of continuous rolling has been established, whereby the barrel has been rolled 

 to its exterior form at one heat by passing it through a number of rolls placed 



