310
MODERN
GUNS
BREECH
AND GUNNERY~
ACTION.
Both the wedge and the eccentric screw are si~ple, strong a~d durable. But the latest model of swinging block is more powerful1n loading and extracting than either of these, and consequently less liable to jams. This action (which has been adopted in our o~n Q.F. equipment and in the American gun) has a single-motion cyhn• drical swinging breech-block. It is set about i" eccentric to the gu~, so that when the breech is closed the striker is not opposite to. t h~ cap in the cartridge till the block has been turned through a ng angle to lock it. This forms an efficient safeguard against prematures occurring in closing the breech. The firing action is a trip-lock, in which the layer, by pulling the firing lever, first draws back the striker and then releases it. . The extractor grips the cartridge both above and below, an? IS actuated by the breech block, which at the end of its swing stnke~ the outer end of the extractor and so causes the'inner end to jerk oU the cartridge. RECOIL
GEAR.
The hydraulic buffer is well established as an efficient meanS of checking recoil. It consists of a cylinder 2.75" in outside diamethe:~ and 0.3" thick, attached by a horn to the breech of the gun. In t 1 works a piston, the front end of the piston-rod being attached to t~e carriage. When the gun recoils, the cylinder is drawn back and t ; oil or glycerine in the cylinder is forced to flow through the narro S space or windage between piston and cylinder, formed by the groOV~e or ports in the inner wall of the cylinder, thus gradually check~ng t t recoil. The depth of these ports is slightly different at dlffer~~e points so as to keep the pull on the piston rod proportional to varying stability of the carriage throughout the recoil. Boring a buffer for uniform stability is a delicate operation, as D difference of a couple of hundredths of an inch is found to make the difference between a steady gun and one which kicks like a mu s; The correct depth of the ports at each point is determined by the Uce of the buffer gauge, first introduced by the Elswick Ordnan .. Company.
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----------------------------• NOTR.-The 1906-07 fashions in gun-designing favour the uniform twist.
See page 26.