There are mainly two types primer cap in an ammunition. Rimfire and Centre fire.
In rimfire ammunition, the firing pin crushes the soft hollow rim of the cartridge against the rear of the barrel to explode the priming compound.
Invented in 1845, by Louis-Nicolas Flobert, the first rimfire metallic cartridge was the .22 BB Cap cartridge.
In centre fire ammunition, the priming compound is held in a cup in the base of the cartridge case. Merely striking the base of the cup with a firing pin would do little more than dislodge the priming compound from the cup. An anvil has to be provided for the priming compound to be crushed against by the impact of the firing pin.
An early form of centerfire ammunition, without a percussion cap, was invented between 1808 and 1812 by Jean Samuel Pauly.
In modern ammunition, there are basically three ways in which this is achieved.
These are called the Boxer, Berdan or battery cup priming system.
The Berdan primer was designed in 1866 by Colonel Berdan of the US Army Ordnance Department. In this system, the anvil is actually part of the cartridge case in the form of a small peg in the primer pocket.
Around the anvil are a number of small flash holes to permit the passage of the ignition flame from the primer to the propellant. Due to the ease and low cost of manufacture, Berdan primers are used mainly in military ammunition.
The Boxer primer was developed in 1866 by Colonel Boxer of the Laboratory at the Royal Woolwich Arsenal, England.
In this type of primer, the anvil is a small bent disc of steel which fits into the cup making the primer completely self – contained.
The flash hole in the cartridge case is centrally located and as it is of a relatively large diameter, it is thus quite easy to push out the fired cup with a thin rod for reloading purposes. Boxer – primed ammunition is almost exclusively used in commercial ammunition.
The battery cup system consists of a plain cup with no anvil, which fits into a slightly larger inverted flanged cup containing its own anvil. The flanged cup provides a rigid support for the primer cup and anvil. This self – contained assembly fits into a recessed pocket in the base of the
cartridge case. Battery cup primers are used exclusively in shotgun ammunition.