Cartridge for Schneider 75mm field guns

The Schneider 75mm field gun adopted by the Bulgarian Army in 1904 used fixed ammunition, in which cartridge and shell were a single unit. It was composed by : cartridge-case, propelling charge, screw primer, shrapnel with double acting time and percussion fuze or high explosive shell with percussion fuze. The cartridge-case (1). It was a cylindrical tube of brass, with thin walls and a base 7mm thick. The front of the case was slightly conical, while the base, called the head of the cartridge-case, was thoroughly cylindrical. The head had a housing for the screw primer. A hole was bored through the housing to connect it with the inside of the case. A projecting rim or flange was formed on the head of the case, which was engaged by the extractor arms in the gun breech. The propelling charge (2). It was composed by smokeless powder : 563 g of pyroxylin powder BM3 (Schneider ammunition) or 450 g of nitro-glycerine powder (Krupp ammunition). According with other sources the weight of the propelling charge was respectively 580-570 g and 508 g. The pyroxylin charge was made in rectangular strips of a straw colour, the strips forming a bunch bound on the top and on the bottom with a silk thread. The nitro-glycerine charge was made in form of tables with a diameter of 75mm and a thickness of 1.5mm. At the top of the charge a felt disc was placed to fill the space between it and the body of the projectile and to insure the powder being held against the primer.
The screw primer (3). It was composed by a threaded body (13) with a great hollow inside. On the bottom of the hollow there was the percussion cup (12), with the anvil directly on it (10). On the axle of the anvil there was a tube filled with compressed black powder. Over the anvil there was a cloth disk (9) moistened with soluble gun-cotton. Into the grooves around the anvil was placed thin black powder (4). On the cloth disk was placed a pellet (8) of compressed smokeless powder (Schneider primer) or compressed black powder (Krupp primer). In the middle of the pellet there was a hole filled with fine grain black powder. Another felt disk (2) was placed over the hole, with a celluloid tablet (7) over the disk. The external surface (1) of the tablet was varnished. The tablet was held by the edges of the screw (6).
When the firing pin of the breech struck the base of the primer (14) along with the base of the cup, they bent on the inside. Therefore the powder of the cup struck strongly in the edged part of the anvil, lighting the fire that was transmitted to the powder contained inside the screw primer, through the tube and the hole (15), bored in the anvil housing. The High Explosive Shell. The Bulgarian artillery for its field guns adopted the Krupp thick walled high explosive shells filled with picric acid. They were painted in yellow. The Shrapnel. The Bulgarian field guns used both the Schneider and the Krupp shrapnel, whose structures and action were similar. They were painted in red.

Schneider shrapnel	Krupp shrapnel	Krupp H.E. shell

Cartridge

Shrapnel

T&P Fuze

H.E. Shell