572,667. Ordnance. SMITH, W. H. June 24, 1940, Nos. 6230/41 and 6231/41. Divided out of 572,468. [Class 92 (ii)] Relates to breech mechanism in which to open the breech the breech block A is first moved parallel to the gun's axis and then swung upwardly about an axis E parallel to or coincident with the gun trunnions. According to the invention, eccentrics D are provided on the swing axis E and are connected on each side of the gun barrel Y to the breech block A by straps X and rods F, the eccentrics being moved by an operating-lever C. This lever is first lifted to rotate the eccentrics and move the breech block backwards until it is clear of the gun barrel, further movement of the lever then tilting the breech block upwardly about the axis E to expose the gun chamber for loading. The eccentrics are in dead-centre position when the breech is closed. The lever C is provided with a grip-operated catch G to engage a stop b on the barrel to retain the lever and breech block in the open position for loading, the inserted cartridge being retained by a spring detent k. On closing the breech, a spring plunger N engages a fixed cam Q to cock the firing pin M into engagement with a sear m. The sear is released through Bowden wires by trigger-grips on gun-aiming handles K, L and both handles must be gripped before the gun can be fired. The firing mechanism is protected by a shield U.