THE ROYAL ARTILLERY INSTITUTION. 
489 
On the main shaft in rear of the barrels a cast-iron cylinder, or 
“ cartridge-carrier ” Fig. 4) is fixed. This has ten longitudinal 
grooves, corresponding with the ten barrels. A gun-metal cover, or 
“hopper” ( B , Figs. 1 and 4), hinged at one side, drops over it. The 
cover has a longitudinal slot, corresponding to the opening in the 
“feed drum”* (T 9 Fig. 1), which rests upon the upper surface of 
“ hopper.” As each column is exhausted, the drum is turned round 
by hand until the next one corresponds with opening in hopper.f 
Through this slot the cartridges drop (as the shaft revolves) into the 
several grooves, ready to be pushed by the lock-plungers into the barrels 
corresponding. 
In rear of this, and inside the breech-casing, is placed the “ lock- 
chamber,” which is keyed to, and revolves with, the main shaft. It is 
a cylinder of cast-iron, having longitudinal channels through which 
the “locks” pass. 
Upon the main shaft, again, and against the back of the “lock- 
chamber,” is secured a cast-iron “ rear guide nut,” which keeps the 
parts firmly together. The locks rest partly upon the outer circum¬ 
ference of this nut; and in the grooves on which they fit, as well as in 
the channels in lock-chamber, are small slots, in which run studs on 
the locks, in order to prevent the latter revolving save with the shaft. 
Inside the “ casing ” is a curved gun-metal plate, or cam, by means 
of which, as the shaft and lock-chamber revolve, the locks themselves 
are pushed forward or back. A piece of steel is let into the front of 
this cam, against which the butt of each lock bears at the moment the 
barrel is fired. 
There is also a steel cam, called a cocking-ring, which, as the lock- 
chamber revolves, draws back and then releases a spiral spring acting 
on the “ firing-pin ” or needle of each lock. 
The Loch . 
The lock consists of a steel tube, or “plunger,” about 11 Jins, long, 
the front end of which, for about 4 ins., is smaller in diameter, and 
has only a pin-hole running through it. 
The remainder is hollow, and slotted out on one side. Its breech 
end is closed by a steel plug, or “ butt,” screwed in. 
Inside is a steel bolt, or “ hammer,” having a projection at the side 
which passes through the slot in the tube, while to the front part of it 
is attached a firing-pin, or “ striker,” of steel. 
A spiral spring is placed over the hammer, being retained by the 
“ butt.” 
To the outside of the tube or lock is fixed a steel extractor, having 
* This drum is of metal, fits on a pin ( b , Fig. 4) in centre of hopper, and contains 240 
cartridges, in 16 perpendicular columns or channels. It weighs, when full, 50 lbs. 
f In the smaller Russian Gatling, used with their batteries of this arm for field service, the 
drum is turned by an automatic arrangement—an improvement much required in our service 
Gatling. 
