Fixed Ammunition

Fixed ammunition for guns had come into use in the early 1890’s, after the silk cloth bag which contained the charge (propellant) had been replaced in certain breech-loading guns by a brass cartridge case which expanded when fired and thus acted as a seal for the gases at the breech. This innovation made it possible for guns of small calibre to have the cartridge case joined to the projectile, and the resulting “fixed ammunition” materially speeded up the process of loading.

Most ammunition in use during the 20th Century was fixed; however, some notable exceptions included the 25-pounder Gun, whose ammunition was loaded in two separate pieces; the projectile and propellant charges. This type of ammunition is referred to as "Semi-fixed"; by having a separate cartridge case and projectile, the propelling charge can be altered by the user.