Boxer Primers Explained

The Boxer primer is the most popular primer style used in the US due to its ease of reloading.  It is also the primary choice among military and civilian ammo manufactuers. Boxer primers were patented in England in 1866 and the US in 1869. Their creator was Edward Boxer, hence the name.

How do Boxer Primers Work?

The operating principle is pretty straightforward.  The weapon's firing pin strikes the base of the primer cup, this causes the primer mixture to be crushed against the anvil.  This creates a flash that goes through the flash hole, igniting the powder in the cartridge.

Boxer PrimerToday, these primers  are created by the million in various factories around the world. They are typically used with brass casings, and are found in sizes discussed here: 

Boxer Primer Sizes

There are four sizes of Boxer primer available today for reloading and they are:

0.175” or 4.45mm - Small diameter pistol or small rifle primer. Examples are .38 Special and .223 Remington.

0.209” or 5.31mm - Shotgun shell and muzzleloader primer. Examples are 12 gauge and 20 gauge shotgun ammo.

0.210” or 5.33mm - Large rifle or large pistol primer. Examples are the .308 and .44 Magnum.

0.315” or 8mm - These are exclusive to the .50 Browning Machine Gun and variations.

The primer size is determined by the cartridge’s primer pocket, which is the opening at the bottom of the cartridge case.  A difference you can see when comparing pistol and rifle primers is how thick the primer’s casses are. Pistol primer cases won’t be subjected to as much pressure as their rifle counterparts so they will be a tad thinner and be easier to ignite by the firing pin.

Boxer cases don’t accept Berdan primers and vice versa, this is due to the anvil being a permanent part of the berdan primed case.  So the Boxer primer simply won't fit into a Berdan case.  With that being said, reloading enthusiasts can get them to work with each other through a labor intensive and rather complicated process.

It’s much easier to simply use the proper case with the proper primer in the first place. This reloading issue is one of the main reasons shooting ranges almost exclusively use Boxer primers and brass casings. Some of the more commonly found primers are made by: Remington, CCI and Winchester

Primers give today's shooter a huge advantage over other methods of ignition.  They are reliable, weather resistant and can be stored for an indefinite period of time.