Arguably the best all round field gun in use by the British Army in the Second World War was the 25 pounder. The 25-pounder fired “separate”or two-part ammunition—the projectile and the propelling charge in its (usually brass) cartridge case with its integral primer were loaded separately. The following description of the case comes from the 1940 handbook for the gun:
The Mark II case is of solid-drawn brass slightly tapered from the base to within 1.1 inch of the mouth, where it is cylindrical. The base is recessed, bored centrally and screw-threaded to receive the percussion primer; it projects circumferentially to form a rim by means of which the extractor of the breach mechanism automatically ejects the case when the breech is opened after firing.
I have just one of these cases in my collection:There were two types of cartridge. The “normal” cartridge contained three cloth charge bags (coloured red, white and blue). White or blue bags would be removed from the cartridge to give “charge one” or “charge two”, leaving all three bags in the cartridge case gave “charge three”. The cartridge case was closed at the top with a leatherboard cup. The second type of cartridge was “super”, which provided one charge only. The cup could not be removed from the cartridge case. In 1943, an incremental charge of 5.5 oz (160 g) of cordite (“super-plus”) was introduced to raise the muzzle velocity when firing armor-piercing shot with charge super; this required a muzzle brake to be fitted. Adoption of “upper-register” (high-angle) fire needed more charges to improve the range overlap. This led to the development of the “intermediate increment” of 4oz cordite, which was introduced in 1944. The bags were striped red and white to indicate that they should only be used with charges one and two. When one bag was used with charge 1 it provided charge 1/2. When one was added to charge 2 it provided charge 2 1/3, and two bags, charge 2 2/3. This allowed a range of seven different charges instead of four.Like all British shell cases, mine has a wealth of headstamps on the base:From these we can see that the shell casing was manufactured in 1942 and includes the lot number so a faulty batch of ammunition and casings could be tracked down later by the markings. In this photograph of an Australian 25 pounder at El-Alamein in 1942, a large pile of discarded shell casings can be seen in the foreground: