Handbook for Light Artillery

The body of the gun is made from a single forging of oil-tempered and annealed steel. The trunnion-ring is screwed on the gun-body just forward of the reinforce, and provides a support for the front sight. The bore is rifled with a uniform right-hand twist. The lands are very narrow in proportion to the grooves, and are ten in number.

The Breech-block is a solid prismatic block of steel with rounded corners, having a horizontal movement in a mortise cut completely through the breech of the gun. The front face of the block is perpendicular to the axis of the bore, whilst the rear face is slightly inclined. The left end of the block is bored to form a prolongation of the chamber when the breech is open, and its front upper corner is cut away to allow free movement of the extractor.

The horizontal movement of the breech-block is limited by the stop-bolt, which, passing through the breech of the gun, engages in a guide in the upper part of the block.

In the right end of the breech-block is mounted a shaft on which is secured the locking-screw, and which terminates in a handle for manœuvring. The thread of the locking-screw is cut away for about 100°, in such a manner that the breech-block may be locked or unlocked by a half-turn of the handle.

The Extractor is a single piece of steel working in a longitudinal groove in the top of the breech-mortise. Its forward end is formed into a claw to grasp the head of the cartridge. On the same side as the claw is a stud which, following a groove in the top of the breech-block, imparts motion to the extractor.

The Vent is a cylindrical channel passing diagonally through the breech and breech-block, and changing direction in the block so as to follow the axis of the bore.

The friction-primer cannot be inserted until the two parts of the vent are in prolongation from the complete closing and locking of the breech-block. The ordinary friction-primer is used.