Gun Basics for Writers: Modern Ammunition Basics, Part 1 of 2

I promised in my last gun basics post that I’d do a post on ammunition.  Here I’ll cover the very basics of vocabulary for modern ammo—there’s a lot more to know about ammunition, but this should get non-gun people started.

This post will be about the parts of an ammunition round.  Part 2 will cover the concept of caliber.

First, a little history.  Ammunition has gone from musket balls that were packed in a barrel with gun powder through an evolution that has led to modern cartridges.  Metal cartridges like those we use today started to be developed in the mid-nineteenth century and were adopted through the latter half of the 1800’s.

Handgun and Rifle Cartridges

A modern round has four parts: the primer, the powder, the casing, and the bullet.  The casing is a cylindrical tube that holds everything together: the primer is in a tiny cap on the back of the cartridge and is what the firing pin drops onto, the powder goes inside the casing, and the bullet is at the other end of the casing from the primer, like so:

Diagram of an ammunition cartridge

Ammunition cartridge diagram (Wikimedia Commons / public domain).
The firing pin hits the primer (5), which ignites the powder (3) which propels the bullet (1) out of the barrel. The casing (2) is left behind.
(The rim (4) generally allows for extraction of the casing; you wouldn’t need to worry about this in most fiction writing.)

When the gun is fired, the firing pin hits the primer.

.303 ammunition

.303 round / public domain. When you turn the round to look at it end-on, you can see the primer.  In the long view, you can see the full length of the casing and the bullet protruding from it on the left.

The primer is pressure sensitive, and ignites in a tiny explosion that sets off the gunpowder inside the cartridge.  The powder goes off in a much larger explosion, propelling the bullet out the other end of the cartridge and in turn out the barrel of the gun:

Bullet being fired

You can see the bullet being propelled out of the barrel here; notice that it has come free of the casing, which has remained behind. Photo by Niels Noordhoek / Wikimedia Commons / CC-BY-SA.

The casing, now empty (the powder has burned up and the primer is punched and no longer active) is left behind when the bullet is propelled away.  After the gun fires, you have a casing that is either left in the gun (for revolvers, bolt-action rifles, etc.) or ejected from the weapon (for semi-automatic or automatic firearms).  Here’s a casing being ejected out of a automatic assault rifle as it fires:

Casing being ejected from an M4 as it fires. Wikimedia Commons / public domain.
For more on the process of how assault rifles fire, see my post on rifles.

Here’s what a casing looks like after the round has been fired; it’s just a bit of brass:

Empty casing. Wikimedia Commons / CC-BY-SA.

The above photo is a handgun casing, and is much shorter than the rifle casing being ejected in the previous photo.  Here is a photo of some rifle casings:

Empty rifle casings. Notice that the primer on the end of the casing on the right has been indented, or “punched,” by the firing pin, leaving it inert.
Photo by D-Kuru / Wikimedia Commons, CC-BY-SA-3.0-AT.

The bullet is gone now, and the powder, which was inside the casing, has been all burned up.

Speaking of the bullet, it has now flown into whatever target the gun was pointing at.  The bullet is distinct from the round as a whole:

Cartridge and bullet

On top is a full 5.56 cartridge; you can see the bullet poking out of the end of the casing on the left. Below it is the bullet alone; this is the projectile that ends up in the target. Wikimedia Commons / public domain.

That is the only part of the round that is propelled forward.

Once again, once the round has been fired, the primer and powder are dead and gone, leaving the empty casing with the shooter.  The bullet, and only the bullet, in whatever was targeted.[1]

The casings are sometimes called “brass,” as they are made out of brass, or “shells.”  So you might talk about “the brass ejecting” or “the brass hit me in the face” or “clean up your brass when you’re done shooting;” you could also talk about “shell ejection” or “the shells eject out the right side of the gun.”  “Brass” is slightly more colloquial but I hear all three a lot.

The full cartridge is usually called a “round.”  These rounds are often colloquially referred to as bullets, which is not technically correct (the “bullet” is technically only the projectile part of the round) but is understood, and many people do it (for instance, one shooter at the range asking another to hand her a few bullets would not strike me as incorrect, even though she’s really asking for a few full cartridges, not just the bullets).

However, what IS wrong is referring to a blank round as a bullet.  Blank rounds are the entire cartridge (primer and powder inside a casing) but WITHOUT the bullet.  Instead of a bullet, sometimes a blank will have a paper wad that is shot out the muzzle of a weapon instead of the metal bullet, and sometimes the brass of the casing will be crimped together to hold the powder in but there’s no projectile fired out of the weapon at all:

Blank rounds. These are crimped blanks; notice that the bullet is missing and the casing is crimped together at the end instead to keep the powder in. Photo by Major tom at Wikimedia Commons, CC-BY-SA.

When a blank is fired, the primer ignites the powder, as per usual (some blanks have a lesser powder load than live ammo; some (full-load blanks) have the same powder load as live ammo).  However, no bullet is propelled out of the gun; you just have the flash and noise of the powder explosion and possibly the expulsion of the paper wad if it’s a type of blank that has one.  It should be noted that BLANKS ARE STILL DANGEROUS within certain distances, because you’re setting off an explosion that is sufficient to propel a bullet at deadly speeds, so even the air coming out of the gun packs a good deal of concussion.

After a blank is fired, the empty casing is with the shooter, as with a live round, but there’s no bullet in the target.  Casings from crimped blanks look obviously different from those off live rounds, because you can see where the brass was crimped on the end before it burst open with the explosion of the powder.

A dummy round is the casing and bullet (though sometimes a fake-looking bullet substitute to make it obvious it’s not a real round) but has neither the powder inside nor the active primer.[2]  It’s basically something that looks like a live round but isn’t; it’s just an inert piece of metal that can’t go off.  So, to summarize: a blank is a round without the bullet, and a dummy is a round with a bullet but without the powder or primer.

Summary for writers:

  • The main things you will probably have to worry about are the differences between a full round, a bullet, and the casing.
  • At a crime scene, the bullet and only the bullet will be found in the target.  The casings may or may not be found near where the shooter was standing, depending on the type of gun and whether the shooter took them with her.
  • During a firefight, the casings (or “brass” or “shells”) may be ejecting out the side of the weapon, depending on the firearm.
  • Blanks look different from live ammo.  A character who knows what ammunition looks like would not confuse them.
  • It is possible to make a dummy round that looks like a real round but is inert.  This round would be easily confusable and could be loaded into the weapon, but would not fire when the trigger was pulled.  (Some dummies are purposely made with differences, such as a punched primer or a different-looking bullet, but it would be possible to make an exact replica.)

Shotgun Shells

Shotgun rounds are usually called “shells” and fire either “shot” or “slugs” instead of bullets.  They look like this:

Here are some shotgun shells. They can come in all sorts of colors, and also several different sizes (more on that in the next post). Wikimedia Commons / public domain.

Like handgun and rifle cartridges, shotgun rounds have a primer and have powder packed inside, but the rest of the shell is filled with a lot of tiny gravel-sized pieces of metal (“birdshot”), a handful of pebble-sized pieces of metal (“buckshot”), or one huge chunk of metal that fills the whole shell (a “slug”).  Here’s a cross-section of one packed with birdshot:

Cross-section of a shotgun shell. Notice the primer on the left end, the powder packed above it, and the shot packed above that.  Wikimedia Commons / public domain.

As you can see, the anatomy of the cartridge is very similar to the anatomy of handgun / rifle cartridges, and they work the same way.

As explained in my post about shotgun basics, when a shotgun is fired the shot spreads out a bit.  Birdshot pellets are shown in the drawing above; here is a photograph of a see-through shell with birdshot inside:

Shotgun shell with birdshot. You can also see the powder below the birdshot that will ignite to propel the shot out of the weapon. Wikimedia Commons / public domain.

Birdshot is the tamest type of shotgun ammunition (and gets its name by being appropriate for hunting birds).  Buckshot looks like this:

Shotgun shell packed with buckshot. Again, you can see the powder below the shot that will ignite to propel the shot out of the weapon. Wikimedia Commons / public domain.

Even though there are fewer projectiles (they’re bigger so you can’t pack as many in), the shot is heftier and therefore has more stopping power (it gets its name by being appropriate for hunting deer).  Finally, this is a slug:

Shotgun shell, partially cut away so you can see the slug. You can think of this like a REALLY BIG BULLET, although it wouldn’t be called that. Wikimedia Commons / public domain.

You don’t want to get hit with one of these.

You can fire blanks out of shotguns as well.  Like with rifle / handgun cartridges, a shotgun blank is a shell without the shot or slug—it has only the powder packed in by a paper wad; the rest of the shell is empty.

Like with handgun / rifle ammunition, the case (which is plastic instead of metal for a shotgun, usually) is left behind in the gun when the shotgun is fired.  For a pump action shotgun, it pops out of the shotgun when the next round is pumped in.  For some reason, I rarely hear this referred to as a “casing;” most often I hear it called a “shell” (which is also the name for the whole round) or “spent shell,” and sometimes the “case” or the “hull.”  Here are some spent shells; you can see where the case has burst open on the right end when the round was fired:

Spent shotgun shells. Photo by Arz / Wikimedia Commons / CC-BY-SA.

If you go to a place where shotguns are fired a lot, the ground will be littered with a rainbow of cracked and crushed plastic shells underfoot.  It’s quite striking.

Summary for writers:

  • Shotgun shells should be referred to as “rounds” or “shells,” and the projectiles as “shot” / “slugs” (whichever is appropriate) or the type of shot (“birdshot” or “buckshot”).  You would not call shotgun ammunition “bullets.”
  • Like with handgun / rifle ammunition, the cases stay behind, and depending on the shotgun might be ejected out or not.  A pump action shotgun would eject the spent shell when you pump it after firing.
  • Shotgun shells can be all sorts of colors.  Red, green, blue, black, white . . .
  • Shotgun shells usually feel pretty weighty when you pick them up; for a twelve-gauge they’re a decent size and are packed with lead, so, pretty dense!  Spent shells, on the other hand, are very light, as they are shells of thin plastic with nothing left inside.

Finally, here’s a photo of all different sorts of ammunition for comparison:


Handgun ammo on the far left, rifle ammo in the center, shotgun shells the two on the far right. Photo by Bobbfwed / Wikimedia Commons / CC-BY-SA-3.0.

I’ll get into the different sizes here in the next post on this series, which will be on caliber and gauge.  As always, please ask if you have any questions!  And since I know I’ve gained quite a few new readers lately, I’ll mention that the other posts in this series always remain open for questions or comments as well.  Also of course feel free to chime in if you have different experiences or happen to know about regional differences or want to share your own experiences with weaponry.  I always like learning more myself!

  1. Shooters may feel this is obvious, but I get asked a LOT what “part” of the round ends up in the target, so I want to emphasize that it’s only the bullet.  And more than once I’ve seen crime shows pull a whole round (with casing intact, instead of just the bullet!) as evidence from the scene of a shooting.  Not so obvious for people who don’t handle weapons!
  2. Usually a dummy has a punched primer so it can quickly and easily be differentiated from a live round, but it’s certainly possible to construct one with some sort of fake cap where the primer would go that appears to be unpunched primer but is inert metal.

6 thoughts on “Gun Basics for Writers: Modern Ammunition Basics, Part 1 of 2

  1. Nione

    Now I can, with complete confidence, smack down the people who tell me that what I have hanging on my wall is not a .44 bullet but rather just the slug. It’s the bullet, period. (Dug out of a piece of wood after being fired at a shooting range.) And I can reference the site of the snarky gunslinging mathematician!

  2. slhuang Post author

    What?? People tried to correct you and say that a bullet wasn’t a bullet????

    Uh….no. They’re wrong. And if you don’t just want to quote me, here’s Wikipedia:

    “The word ‘bullet’ is sometimes colloquially used to refer to ammunition in general, or to a cartridge, which is a combination of the bullet, case/shell, powder, and primer. This incorrect use of ‘bullet’ when ‘cartridge’ is intended, leads to confusion when the components of a cartridge are discussed or intended. See the reference section for more detail.”

    ::dusts off hands:: Glad I could help you win a RL argument. It’s what I’m here for.

  3. InMyBook

    This clarified so much in my mind. I finally now have a grasp of what regular ammo is and how blanks and dummies differ. This is such a clear and comprehensive review. Now I never have to fear being smacked down because I have been clueless and mistaken someone’s bullet for a slug. Ignorance is not bliss.

  4. slhuang Post author

    Actually, pistol and rifle bullets are sometimes referred to as slugs, but I don’t hear it often. :) (And in certain contexts it would sound wrong to me, but unfortunately I’m not sure how to define when it would!)

    Glad you felt this was clarifying!

  5. Pingback: Kuasa Impak & Tenaga Sebutir Peluru | Jom Science & Tech

  6. Pingback: State of the Blog 2^8 | SL Huang

Comments are closed.