7.7 x 56R : [GB] Cartridge, SA, Ball, .303-inch, Mk 7
priming cap : attachment : press fit
Reference: War Office : 1936 : Text Book of Ammunition : HMSO : : p 7. Description: Mark VII (7) Ball was originally approved in March 1910. It was loaded with a 160 grain spitzer bullet, but this very soon proved to have inherent accuracy problems. In November 1910, a version with a 174 grain composite spitzer bullet was approved for land and naval service, this approval being extended to air service in May 1919. This bullet was of composite construction, with a two-part core, the upper part being aluminium, the lower of lead/antimony alloy. Bullet jackets were mostly either cupro-nickel or gilding metal, but steel jackets were authorised at various times, as were wartime substitutes for the aluminium in the core. The round was very satisfactory, and remained the standard issue ball load for the remainder of the .303's service. The purple primer lacquer was approved in 1918. From 1915, the primer of Mark VII was 'ringed in', following instances of primer blow-out in Hotchkiss machine guns when the primer was only a press fit.