A primer is a small, explosive metal disc inserted into the rear of a cartridge. Its purpose is to ignite the gunpowder charge that sends the projectile (bullet or shot shell) flying through the air towards its target.
Understanding how primers work is an integral part of learning how to reload ammunition.
How Primers Work
Modern manufacturers use two different designs for incorporating primers into their ammunition:
- Rimfire Primers – the primer is an integral part of the cartridge. This type of ammunition cannot be reloaded.
- Centerfire Primers – the primer is inserted into the brass casing and is removable. This type of ammunition can be reloaded.
Of these two, the centerfire design is far more common, which is good news for reloaders.
Tips for Handling Primers
Primers are generally safe when handled properly. Here are some tips to keep in mind:
- Store your primers in their factory packaging until they’re ready for use – pouring them into a separate container can cause them to detonate.
- Always wear vision protection while reloading ammunition – otherwise, an exploding primer can drive metal fragments into your eyes.
- Make sure you’re always alert and attentive when handling primers – fatigue and distraction can lead to serious, sometimes fatal mistakes.
- Avoid using ammunition manufactured during or prior to World War II – primers from this time period might contain dangerous corrosive chemicals. For the same reason, you should avoid ammunition made in Russia or China.
- Follow the instructions in your reloading manual to the letter – deviating from these directions can expose you to serious safety risks.
History of Primers: From Match Locks to Modern Ammunition
Back in the 1600s, loading and firing a gun was a slow, laborious task. First, the shooter poured black powder down the weapon’s barrel, followed by a scrap of fiber wadding and the musket ball itself.
The next step was to pour a small amount of priming powder into an opening at the weapon’s breach called the “touch hole.” Extreme care was needed to keep moisture and dirt out of the mechanism.
Pulling the trigger caused a slow-burning fuse known as the “match” to ignite the powder in the touch hole, setting off a chain reaction that fired the weapon. This entire process could take more than a minute, making each shot precious.
Weapons technology took a giant leap forward in the early 1800s, with the introduction of small, self-contained primers known as “caps.” This eliminated the need to pour powder into the touch hole, simplifying gun design and greatly increasing the rate of fire.
By the end of the 19th century, further advances combined primer, gunpowder, casing, and projectile into a single self-contained unit known as a “cartridge.” This led to the invention of modern automatic and semi-automatic weapons.