THE ROYAL ARTILLERY INSTITUTION. 
309 
cock. When the trigger* is pulled the spring is released,, and forces the 
striker forward on to the cap in the cartridge. When the lever is pulled 
down the block falls, and in doing so opens the breech and strikes against 
the lower limb of the extractor (a bent lever), and causes it to eject 
the empty cartridge by means of the catches on its upper limb, which 
work against the projecting iron base of the cartridge. 
The Barrel of the Martini-Henry is of steel—a metal which, owing to 
its greater strength, elasticity, and hardness, is much superior for the 
purpose than the wrought-iron hitherto used. The old objections to steel 
were its brittleness and the difficulty that existed in welding on the 
nipple lump. Neither of these objections exist any longer; the latter 
being removed by the introduction of breech-loaders, and the former by 
improvements in the manufacture of steel to such an extent that not 
one in 50,000 finished barrels fails at the proof—which consists of one 
round with a double charge of powder and a bullet equal in weight to 
1^ the service bullet. The steel is supplied by the contractor in rough 
barrels—simply cylinders of sufficient size, with a hole through the 
centre. 
The rough barrel undergoes the following principal operations :— 
1. Boring. 
2. Turning, 
3. Bifling. 
4. Chambering. 
5. Gauging. 
6. Sighting. 
The boring is done gradually, the concentricity and regularity of 
the work having to be repeatedly tested by “ shading”— -i.e. } holding 
up the barrel to the light and noticing the appearance of the shadow 
thrown down the bore by a black board at the top of the window. 
Any irregularity in the barrel would be indicated on the edge of the 
shadow. 
Turning is cutting off the exterior surface, and is performed in a 
lathe; the barrel being kept steady to the action by bearings in solidified 
resin, which is poured around it when in a liquid state and is easily 
knocked off when the operation is over. 
Bifling is performed in a machine furnished with a tangential bar 
which guides the cutter bar down the bore at the proper angle of the 
rifling. As the grooves are “ progressive 33 for 11 ins.—that is, deeper 
at the breech than towards the muzzle—there is an arrangement by 
means of which the cutter is screwed gradually down as it cuts its way 
up the bore for that distance, after which the depth remains the same 
throughout. 
The barrel is rifled with 7 grooves, *03 in. of the original bore being 
left between adjacent grooves as lands, so that a section of the rifled 
bore presents the appearance of a heptagon with acute re-entrant angles. 
The twist of the rifling is 1J in the length of the bore, or 1 turn in 
22 ins., and there is a machine for testing the spiral. 
* Tlie trigger “pull-off” is equivalent to a weight of 6 to 8lbs. (See clause 144 Army Circular, 
1st October, 1875.) 
