Ammunition Anatomy

I really wanted to call this Anatomy of a Bullet, but that's technically incorrect, and I'll explain why below.

As I'm shooting, I tend to think of questions, rather than keeping my mind on what I'm doing.  Maybe that's why I keep missing? Anyway, I figure the best way to get these questions out of my head is to answer them.  Today, we are going to look at the anatomy of ammunition!  I'm specifically looking at centerfire rounds, though the principles are the same for rimfire and shotgun shells.

There are four basic parts to each round.



1) Casing

From Starline Brass

Cartridge cases are generally brass.They contain the powder and primer and hold the projectile in close proximity to these explosives.  The crimp is the part of the cases that crimps or curves inward to hold onto the projectile.  The head (closed end) of a casing seals the back of the chamber to force the gasses forward and expel the projectile.  The base of the casing has a rim that is gripped by the extractor to remove the empty casing or to prevent the round from moving to far into the chamber of a revolver.

2) Projectile

This is the bullet, and why I couldn't title this post anatomy of a bullet, as that would be over fairly quickly.  I'll have to get to ballistics eventually though!  Most bullets are made of lead and some have copper or other jackets. In general, bullets are designed to expand on impact.  There are frangible (breakable) and other types of specialty rounds for unique uses.

3) Powder
Powder is the general term for the compound that produce gasses to push the projectile out of the barrel.  Historically this was black powder, which is a combination of charcoal, sulfur and saltpeter.  Most modern powders are 'smokeless' compounds of nitrocellulose and/or nitroglycerin

4) Primer
This is the collective term for the chemical primer compound, cup and anvil which is located int he head of the case.   When the primer is struck, it ignites the priming compound.  The flame travels through the flash hole to ignite the powder. 




How does it all work together?

• The firing pin impacts the primer
• Ignition of the priming compound
• Flame moves through the flash hole of the casing
• Ignition of the powder
• Burning powder creates large amounts of gas that expand the case to seal the chamber 
• Gasses push the bullet down the barrel 

If you'd rather see this information in video form, check this one out.