Centerfire ammunition uses primers as the primary ignition for the firing of a cartridge. The primer consists of a cup full of a primary shock sensitive explosive. In Berdan primers there is an anvil in the cartridge case and two holes or vents for the burning primary mixture to have access to the powder charge. In Boxer primed ammo there is one vent hole and the anvil is incorporated into the primer. The firing pin strikes the primer and dents the cup. The priming mixture is crushed between the deformed cup and the anvil and ignites, blowing through the vents it ignites the powder.
Reloading Berdan & Boxer Primers
Hiram Berdan was an American inventor and developed the Berdan primer. Berdan’s invention is extremely popular in European ammunition, military ammo in particular. With two vents Berdan primed cases are difficult to reload, possible, but difficult. Edward Mounier Boxer or the Royal Arsenal in Woolwich, England invented the Boxer primary used in US ammo as it facilitates easy reloading. It is common in both sporting and US military ammunition. As such we have the following:
Small Pistol 0.175 38/357 Magnum, 9mm
Large Pistol 0.210 45 Colt, 45 ACP, 44 Magnum
Small Rifle 0.175 223 Remington/5.56 NATO
Large Rifle 0.210 308 Winchester/7.62 NATO
5O BMG 0.315 .50 Caliber 12.7 x 99mm Browning Machine Gun
Shotgun 0.209 12, 20 and 410 shotgun
Different primer manufacturers designate their products by number such as alpha-numeric identifiers. CCI tends to use three digits, while many use integers and fractions like Remington. Winchester uses alpha characters for metallic ammo and alpha-numeric for shotgun primers or a numeric system as well in the past. There is no standardization.
Priming Mixture Composition
Primers are filed with shock sensitive mixtures of explosive, albeit in small amounts. Early primers used mercury fulminate as the mixture. Most early primers were corrosive to the bores and require cleaning of the firearm shortly after usage as the residue is hydroscopic or attracts water. Non-corrosive primers appeared in the 1920’s for sporting ammo, but most militaries used corrosive priming and much European military ammo still does. Lead styphnate with barium nitrate. Lead free primers are making an appearance but military tests show that accuracy suffers, and corrosive primers for the military are used because they are more reliable and store better, at least in eastern and European military loadings. The only place where leaded primers may be a health factor is indoor ranges. Most lead-free primers are coming out of Russia and South Korea. As accuracy is a paramount consideration in ammo as well as reliability, lead-free primers are not popular. But that being said the chemists’ soldier on trying to find a reliable lead-free solution. Most conscientious shooters tend to clean their weapons shortly after use anyway. Modern boxer ammo uses non-corrosive and non-mercuric primers. Magnum primers just offer hotter priming mixtures to ignite compressed charges of hard to light smokeless propellants in magnum cartridges.
Percussion Caps & Primers
The primer being the ignition factor in ammunition is an essential item. Percussion caps and primers are the standard, though there have been attempts at electrically initiated primers, but they have not caught on. Faster lock time of electrical primers would be useful to competitive shooting sports, but then there is the added expense of incorporating a source of electrical current. Batteries or piezo-electric sources are problematic in their own right.