The Palliser construction is entirely applied to the conversion of old cast-iron smooth-bore guns into efficient rifles. In this system the bore of the gun is reamed out to a sufficient diameter to permit the insertion of a coiled wrought-iron tube. This tube is made up of a number of short coiled sections end-welded together. The rear of the tube is planed down, and a jacket (coiled with the spirals opposite in direction to the tube) is shrunk on. The breech end of the tube is closed by a wrought-iron disc screwed into place. The surface of the tube is then turned to a snug but not tight fit in the casing or gun, and is inserted, being held in place by a muzzle screw-collar. A screw is tapped through the chase into the tube to keep it from turning. The old vent is bored through and the gun is submitted to a course of proof-firing with full charges, to expand the tube against the wall of the casing, making a snug fit. A spiral slot is cut around the tube from front to rear, and carried through the cascabel as a tell-tale for the escape of gas in case the tube is split or cracked through at a weld. These guns are extraordinarily long-lived, and have been extensively used by the governments of Great Britain and the United States.
Palliser Projectiles. [See Pages 208-210].
WHITWORTH CONSTRUCTION.
Whitworth Muzzle-Loader.
Whitworth ordnance is used almost exclusively in the Brazilian Navy, and is the regulation type. The Whitworth construction belongs to the all-steel type, and differs in almost every particular from the other types. The guns are both muzzle and breech-loaders. The body of the gun consists of a steel tube reinforced by steel hoops. The tube is cast solid and submitted to a heavy hydraulic pressure while in a molten state, giving the metal as it solidifies a perfectly homogeneous crystallization throughout. This tube is bored completely through, and in the muzzle-loaders the breech end is closed by a steel screw-plug. The hoops are hollow cast and forged on a mandrel, the lengths in the different layers being accurately turned and screwed together; the layers are then put on the gun cold and forced home (from the muzzle end) by hydraulic pressure, the forcing being carefully gauged so as not to crush the metal of the tube.
Whitworth Breech-Loader.
The breech-loaders are slotted across the rear face in such a manner that the rear face of the block is entirely exposed, thus saving in length of breech of gun. The breech-block is cubical, and is traversed along the upper and lower surfaces by heavy threads set at an angle with the face of the block. These threads travel in heavy male threads in the slot, the system forming the support for the thrust on the block. Attached to the rear face of the block is a weighted crank which revolves a cogged wheel housed in the block and travelling in a rack in the rear of the lower side of the block-seat. In guns of heavy calibre the system is reversed, the crank and wheel housing in the rear of the gun and the rack in the block. By means of this gearing the block is moved transversely, masking and unmasking the bore, the left end of the block being cut for a loading-hole. A stop on the face of the breech locks the block when home and catches it at the proper point when open.
