Ammo Primer Types

Ammo primers may be broken down to two main types:  both rimfire and centerfire versions are popular today. Rimfire denotes the type of priming agent used. Rimfire is so called because the firing pin strikes the cartridge base’s rim. Centerfire is operated by the firing pin striking the primer cap at the center of the base of the cartridge to ignite it. Here is a list of the Ammunition Primer types:

Rimfire Primers

Rimfire priming system is primarily used in small .22 caliber ammunition. Rimfire was popular before the advent of Centerfire priming and is still used in some Cowboy Action shooting. Rimfire ammunition is not reloaded.

Small vs Large Primers

There are two main types of primers in use today. Small Primers (.175”) are used for pistols calibers up to .357 Magnum (when using slower burning powder) and rifle calibers up to .223 while large primers generally apply to the larger calibers.  Here is a brief overview for reference:

• Small pistol primers - Used for 25 ACP, .32 ACP, 40 S&W and all variation of the 9mm (including 380)
• Small rifle primers - Used for .223/5.56 and smaller
• Large pistol primers - Used for 45 LC, .45 ACP and 10mm
• Large rifle primers - Used in rifles with calibers greater than .223.
• Small magnum pistol primers - Used primarily in .357 Magnum loads.
• Small magnum rifle primers - Used in Wildcat loads.
• Large magnum pistol primers - Used in 44 Magnum loads
• Large magnum rifle primers - Used in large caliber rifle rounds