You pull the trigger – and a lot of chemistry and physics takes place in a split second.
Aki Suvilahti from cartridge manufacturer Sako says there are, generally, three different types of primer. For calibres such as .222 and .223, there is ‘small rifle’ primer, which has low energy.
Next up is what Aki calls ‘large primer’, used for cartridges aournd the .243 and .308 sizes. The magnum calibres such as .300 Win Mag and .3875 H&H need more energy for the primer to ignite the propellant.
When a firing pin hits the primer, the pressure raises the temperature which ignites the priming mixture.
After the primer in the bullet explodes, the propellant shoots the bullet from the gun.
The propellant, or powder, is different for each kind of bullet.
“Usually for bigger calibres – heavier bullets – we have to use a different kind of powder,” says Aki. “Usually it’s slower burning powder and with the small ones it’s higher energy content.
“It comes down to the question: what is the case volume and what kind of bullet weight do you have? Of course what is the pressure? because there is legislation that limits the use of pressure in specific calibres.”
Sako uses about 20 different powders, depending on the calibre. Constantly-changing calibre technology means the company has to keep on its toes, updating and creating new propellants to meet demand.
“For different calibres, different bullets, there are powders that work better and powders that don’t work,” says Aki. “You have to find the optimal one to have good muzzle velocity and accuracy and remain in the correct pressure area.”