The Complete Bullet Guide – Bullet Size Chart, Bullet Types And More

Bullets are just bullets right? The complicated part is the actual gun, right? Turns out there is actually a lot of technical details that go into bullets. There are so many different bullet calibers, sizes and types that it can really make your head spin!

So to try and help those folks out that want to know more about what the best bullets are to use in their gun, we put together this guide that looks at what bullet names mean, a bullet size chart comparing the most common bullet calibers, and what the different types of bullets are that are available to us.

How Bullets Work

Below is a video that shows an animation about how a bullet actually works when it is fired from a gun.

Bullet Naming Convention

Before we can effectively interpret a bullet size chart, we need to understand the naming conventions used when referring to ammo. Sometimes when we talk about ammo, it sounds like we are at an IT convention or something with all the acronyms! So why do we name ammo the way we name them?

Unfortunately there is no central standard for the way bullets and ammo are to be named. So manufacturers typically each decide themselves how they will name their ammo. However, there is at least usually some logic applied to how ammo is named.

For example, some ammo are named according to their metric diameters, where the bore diameter and length of the casing is specified. A good example is the 7.62×51mm NATO cartridge, which has a bore diameter of 7.62 millimetres and a casing that is 51 millimetres in length.

In countries where the unit of measure is in inches, rather than millimetres, the naming of the bullet often refers to the bullet diameter in hundredths of an inch. For example the .308 Winchester has a bullet diameter of .308 inches.

So that explains the numbers in the naming convention of bullets. But what about the letters in ammo like .22LR and .380 ACP? The LR in .22LR refers to Long Rifle, while ACP refers to Automatic Colt Pistol.

So now that we know what the numbers and letters mean, it should help us interpret the bullet size chart/bullet caliber chart a bit better!

Rimless, Semi-Rimmed and Rimmed Bullets

When we talk about the size of a bullet, we probably also need to look at the rim of a bullet. Most cartridges have some form of rim or ridge (sometimes referred to as a flange). The rim may actually serve a number of purposes, such as providing a lip for the extractor of the gun to engage or even just to provide headspace for the cartridge.

Headspacing is when the rim of the cartridge holds the cartridge at the proper depth in the chamber.

Rimless Bullets

When a bullet is noted as rimless, the rim on the bullet casing has exactly (or at least almost) the same diameter as the base of the bullet casing. As there is not much of a rim protruding, rimless ammo feeds smoothly from box magazines, and are typically not well suited to break-open and revolver actions.

Examples of rimless ammo include 9mm, 40 S&W and .308 Winchester.

Semi-Rimmed Bullets

Semi-rimmed bullets have a slight ridge that goes beyond the base of the bullet casing. Semi-rimmed bullets are not as common as rimless or rimmed bullets, with examples including the .25 ACP and .38 ACP.

Rimmed Bullets

Rimmed bullets are the oldest style of bullet. With rimmed bullets the rim has a much larger diameter than the base of the bullet cartridge, which serves to keep the cartridge in the chamber of the firearm and to hold the cartridge at the proper depth in the chamber.

Rimmed bullets are well suited to revolver actions, and not so very well to guns that feed the ammo from box magazines. Examples of rimmed ammo include .38 Special and .44 Magnum.

Common Calibers - Bullet Size Chart

To help understand the different bullet calibers' sizes, we put together this bullet size chart with the most common calibers included.

CaliberTypeBullet Diameter (In)Case Length (In)
25 ACPSemi-Rimmed0.2510.615
.380 ACPRimless0.3550.680
.40 S&WRimless0.4000.850
.45 ACPRimless0.4510.898
.38 SpecialRimmed0.3571.155

Bullet Types

Okay, so we are now getting closer to know a lot more about bullets than we did before. But to truly understand ammo, we also need to know more about the different types of bullets that are available to us and which bullet types are the best for our specific needs.

Full Metal Jacket (FMJ)

These are typically bullets that have a copper jacket covering the top of the of the bullet, with the core usually consisting of a softer material such as lead. FMJ bullets are traditionally quite cheap to produce, which is why it is so popular for practising at the gun range.

The design of full metal jacket bullets is uniform and aerodynamic, which makes it a good choice for long range precision shooting. However, the design also means that the bullet will keep going through its target rather than stopping. This makes it less ideal for things like hunting or home-defence.

Open Tip Match (OTM)

Sometimes folks mistake open tip bullets for hollow point bullets as they also have an opening at the top. However the open tip bullets have this opening due to the way they are made. They differ from the hollow point bullets in that their openings are too small to actually expand effectively upon impact.

These bullets are favourites among long distance shooters, as the bullets are very consistent (more so than the FMJ bullets).

Hollow Point (HP)

Now we get to the truly deadly bullets. The hollow point bullets are designed to expand upon hitting the target and in doing so, provide a lot of stopping power. This also means that the round does not travel through the target, potentially hitting a secondary unintentional target.

If you want a bullet for self-defence purposes, this is the bullet to go for!

Soft Point (SP)

The soft point bullets try to make use of the advantages of the FMJ bullets, but that does not go through a target as easily. This is achieved whereby a part of the tip still has the soft lead exposed. The idea is that this soft lead tip will flatten upon impact with the target. However, modern ballistic tip bullets (mentioned below) provides better performance than the soft tip bullets.

Ballistic Tip

If you want the advantages of the FMJ bullet and the hollow point bullet in one, then the ballistic tip bullet is the answer you are looking for.

It has a hollow point that will expand upon impact, but the hollow point is covered with a plastic cap. The plastic cap is shaped to mimic the aerodynamics of the FMJ bullet. So this way you get the stopping power of the hollow point, along with the consistency and accuracy of the FMJ bullet.

Wrapping Up

We hope this article has answered some of your questions about bullets, bullet sizes or just why bullets are named the way they are. If you have any questions or comments, please feel free to leave a note in the comments section below. We would love to hear from you!