The guns described in this and the next chapter are built-up guns made of low steel, and all the parts are tempered in oil.
The tube enters the jacket from the front[3] and has shoulders upon it, which come in contact with corresponding shoulders in the jacket. These shoulders prevent any forward movement of the tube or rear movement of the jacket.
The tube tapers from in front of the jacket to the muzzle, which ends in a swell.
The exterior of the jacket is made up of a series of tapering surfaces.
On the interior surface, starting from the rear end, there are first, the seat for the carrier-ring in the jacket, which also contains the slotted and threaded sectors for holding the breech-block; in front of this is the tapering gas-check seat in the tube; and forward of this is the cylindrical powder-chamber, which is connected to the shot-chamber by a slope. The shot-chamber also is cylindrical and connected with the bore by a slope.
The vent being axial in the model of '90, enters the powder-chamber through and along the axis of the spindle of the obturator. In front of the gas-check seat in the model of '85 there is a cylindrical surface leading to the ellipsoidal powder-chamber, which is connected with the shot-chamber by a slope, and the radial vent enters 12½ inches from the rear face of the jacket and at the maximum diameter of the powder-chamber. The vent-piece, made of copper, is screwed into position, the part projecting above the surface of the piece being rectangular.
The Breech Mechanism.
The principal parts are the breech-block, the carrier-ring, the obturator, the lever-handle, the bronze handle, and the vent-cover.
THE BREECH-BLOCK.