Shrapnel for Schneider 75mm field guns
The shrapnel adopted by the Bulgarian Army was composed by : body with copper driving band, ogival head, diaphragm, central tube, bullets, colophony, bursting charge. It was equipped with a double acting, time and percussion, fuze.
The shrapnel body (1). It was made of steel. Its base contained the bursting chamber, which was separated from the rest of the body hollow by the diaphragm. The inside of the upper part of the body was threaded to screw on the head. The cross-section of the body was slightly smaller than the inside diameter of the gun barrel except for two locations: the top of the cylindrical portion of the shell and the rotating band. The top band was known as a bourrelet. The driving band (10) was made of copper and was pressed into a groove milled near the base. They provided a very close tolerance between the projectile and the barrel. Being larger than the body itself the driving band was compressed by the rifling grooves and rotated the projectile, keeping it in a straight line during the flight.
The head (5). It was made of steel; only some patterns of Schneider shrapnel had the head made of aluminium in order to make it lighter. It was screwed into the end the body and had inside the fuze body screwed in it. At the bottom it had a hole where the upper part of the central tube was fixed.
The central tube (7). It was made of steel with an inner diameter of 8mm. It had to transmit the flame from the primer charge in the fuze, housed in the head, down to the gunpowder stored in the base. It was filled with pellets of compressed cylindrical powder. In the middle it had a hole where the lower part of the central tube was fixed. To make easier the breaking of the tube and the ignition of the colophan, it had some grooves notched on its upper surface.
The diaphragm (6). It was made of steel and was supported by a shoulder in the wall of the shrapnel body, into which it fitted tightly. In the middle it had a hole where the lower part of the central tube was fixed.
The bullets (8). They were
made of hardened lead and filled up the room between the diaphragm and the
head. They weighted
The colophan. It was a pine rosin mixture poured into the shrapnel to hold the bullets in place and to provide smoke so that artillery observer could determine if the shrapnel was timed correctly to explode on the target.
The bursting charge (9). It was
Time & percussion fuze. The Bulgarian artillery, having adopted both Schneider and Krupp shrapnel, used the double acting, time and percussion fuze, of both firms. The general structure and the action of these two double-banked fuzes were very similar, even if their inner arrangements had some minor differences.