SHOUT NOTES ON PROFESSIONAL SUBJECTS. 
159 
100. German 8J-in. Gun. 
(Communicated by Lieut.-Colonel W. E. M. Reilly, C.B., R.A.) 
Construction .—This gun of 8^-in. calibre is a breech-loader, having its breech 
closed by a wedge, in the centre of which is the vent, nearly in prolongation of the 
axis of the bore. It is of cast steel, and consists of an inner tube surrounded by 
nine cast steel hoops, shrunk on. The inner tube is the full length of the gun, 
15 ft. 81 ins., and may be considered of three thicknesses :—Eirst, that about the 
loading-chamber and vent-piece, where there are no hoops. The next portion is 
cylindrical and rather thinner, and reaches to about half the length of the gun. 
This is belted by one layer of five hoops, the rear one of which is very narrow, the 
front ring being broad, and being also the trunnion ring. Round this layer, and 
over the powder-chamber, is a second layer of one broad hoop. The third portion 
of the tube, extending to the muzzle, is conical, and has three narrower hoops 
forming on the exterior surface steps adjoining the five hoops above-mentioned. 
At this junction is a ring, half in the tube and half in the hoops, which prevents the 
tube breaking away to the rear from the system of hoops. 
Weight ,—The weight of the gun is 9 tons, including vent-piece, which weighs 
7\ cwt. 
The axis of the trunnions passes through the axis of the bore. 
There is no preponderance. 
The rifling consists of thirty grooves, whose driving edges have a twist of 1 in 38 
calibres, or 2° 38' 42-6". 
Breech Ring .—At the end of the bore is a breech ring, which is set in an enlarge¬ 
ment of the rear edge of the loading-chamber. This ring is hollowed out to the 
front, so that the action of the gas merely presses it tighter against the enlargement 
in which it is set. 
Wedge .—The wedge is also of cast steel, is very slightly tapered, and enters its 
chamber from the left. In shape it is cylindro-prismatic, its front being a plane, 
its rear semicircular in section. Its motion is effected with great facility by means 
of a screw working in two collar blocks, one at either end of the wedge, which may 
be termed the carrying screw. This screw works against a half female screw in the 
top of the wedge-chamber. The screw is worked by a wrench. On the front of 
the wedge is a circular steel plate of slightly larger dimensions than the height of 
the wedge. This is hollowed out towards the front, and pierced through the centre 
for the vent; but as it is necessary to preserve contact between this plate and 
the breech ring, it can be advanced by placing a thin brass plate beneath it. 
In order to press the face of the wedge firmly against the breech ring, there is in 
a slot in the rear part of the wedge a screw, on which works a collar having three 
teeth on one side of its exterior. When the wedge is home, by a half turn to the 
right, this screw carries the collar round with it, so that its teeth fall into corres¬ 
ponding slots in the side of the wedge-chamber. By continuing the operation of 
screwing, the screw works in the collar (which is now fixed), and thus forces the 
wedge further home, and at the same time its face against the breech ring. On the 
