The Importance of Primers

When a gun discharges, a projectile is set in motion by an explosion of gases, what set the explosion off is what has mad the modern technologies of firearms possible. The smallest part of the cartridge is the primer, yet it is possible the most important. Without a primer the cartridge would be nothing more than a storage vessel for some lead and powder, albeit with a couple of holes in the base.

primers provide the tiny explosion needed to set a cartridge in motion and fire a projectile from its casing, many people only consider then enough to know that they need to be there.

Primers represent centuries of development and design testing. Not only do primers deliver the needed spark to the cartridge they also must be able to present a small forward pressure to set off the burning propellant, but they also must be able to hold the massive rearward pressures to ensure that the gases do not come out the back side of the cartridge. The actual propellant is a careful mix of chemicals that control temperatures, power, and blast.

The mixtures of the propellants usually use powdered Aluminum to help raise the temperature of the explosion to oxidization levels in most modern cartridges. The primers propellant also contains a form of sensitizers to help control the energy required to set off the primer, and of course binders to hold the whole propellant package together during the numerous handling stages and shipping.

During the muzzle loading period of firearms the explosive mix in small arm was mercury fulminate. This compound was fine for the materials used at the time. Not only until the introduction of brass and copper cartridge cases was it noticed that the mercury fulminate released a vapor that caused the case to become brittle. Later the primers mixture was adjusted to use potassium chlorate, this avoided the damage to cartridge brass, proved to be more reliable, and stable than the mercury fulminate mixture. But like all good things there was a down side, the potassium chlorate has a nasty habit of leaving a residue that contained chemicals very similar to common table salt, which rusted out firearm barrels very quickly. Because of this residue with the potassium chlorate primers, these type of bullets have been labeled as corrosive. Once again primers were adjusted for a cleaner better primer mixture, the best to be made was the lead styphnate blended with non corrosive fuels and oxidizers. This combination provided the clean burn, lack of residue, reliability, and stability. Now for over 60 years almost every factory made primer uses the lead styphnate mixture. The lead styphnate primers are known as non corrosive and no mercuric in nature.

Once again the possibility of a perfect primer has been dowsed by doctors, concerns about airborne lead in poorly ventilated areas. With these issues of lead, CCI was the first manufacturer to develop and use lead free primers and market them inside of factory ammunition. Unfortunately these lead free primers are only found in factory loaded ammunition and not sold for home loading. With the lead free primers unique mix of chemicals and characteristics, they are only usable with certain propellant types, and a couple of extra operations are required during the loading process.

Oddly enough there are only two types of primers on the market the Berdan primers, developed in America, and Boxer primers, developed in Britain. Even odder is that almost every country other than the U.S.A. uses the Berdan primers while the U.S. market uses the Boxer primer. The main difference between the two primers is in the reloading capabilities, it take a few more tools to safely remove a spent Berdan primer and replace one that with the Boxer primers, therefore the popularity of boxer primers ha remained a U.S. market especially with reloading.

With the primers being such a core piece of the cartridge it is hard to believe that it is so easily overlooked. With so many years involve with the modern primers development, and numerous hours of testing, overlooking the common primer seems almost criminal.