The Ultimate Guide to Ammunition: Understanding Calibers and Their Uses
When you are standing in front of a gun counter, the most important question you have to answer before you take a firearm home is which caliber you want. While there are usually just a handful of mainstream calibers that many people stick to, there are hundreds of them to choose from. Not every caliber works for every situation, so narrowing in on the ideal one for you depends on what you plan to use the firearm for.
One important thing to realize is that a caliber is not a cartridge, even though many people use those two terms interchangeably. The term “caliber” simply refers to the diameter of a cartridge’s bullet. For example, the low power rimfire 22 long rifle cartridge has a 22 caliber bullet, but so does the much more powerful 5.56 NATO cartridge that you would see in an AR-15 (5.56 mm = 0.224 inches).
To make sure that everyone is on the same page, we will start with a crash course in cartridge anatomy, and then we will dive into different uses for firearms and which calibers you will want to consider for each of them.
Cartridge Anatomy Crash Course
A cartridge is what you pull out of a new box of ammo. It has a casing with gunpowder inside, a bullet, and a primer. The casing is usually brass but can be made of other materials, like steel. At the bottom of the casing, there is a circular primer. When struck by your firearm’s hammer or firing pin, the primer ignites the gunpowder inside, sending your bullet down the barrel and toward your target.
At the end of the cartridge is your bullet, which can be made from a variety of materials, but is most commonly made of lead with a copper jacket. Caliber and grain are two common terms we can use to describe the bullet. Caliber is the largest diameter of the bullet in inches or millimeters, and this measurement is always in the cartridge’s name. Grain is a unit of weight, and it is the only unit we use to describe the weight of bullets. Seeing as bullets come in many different designs, these common measurements are usually where we start when we want to compare two types of bullets.
The bullet sits in the neck of the casing, which holds it tightly. This is important because certain cases have been redesigned to fit different calibers, often by making the neck smaller to use a smaller caliber bullet. These cases are usually referred to as “necked-down” variants of the parent case. One example is the .308 Winchester that was necked down to the .243 Winchester.
.22 Long Rifle
All of the other categories we will talk about have plenty of calibers to choose from, but the 22 long rifle is in its own category in today’s market. There are other small cartridges such as the .25 acp, but they are not nearly as popular. Anything comparable in size to the .22 long rifle is ideal for target shooting and very small game like squirrels. This cartridge is great for fun, target practice, small game hunting, and introducing new shooters to a firearm with nearly zero recoil.
Handgun Calibers
Most commonly, handguns are used for self-defense. Plenty of Americans have an “Everyday Carry” handgun that they conceal carry in public. Concealed carry handguns have saved countless lives, and continue to do so; which is why this category is most likely to be someone’s first firearm purchase.
Handguns can also be used for home defense, often being the exact same firearm that many people use for conceal carry. However, if you have the budget, many people will buy a separate handgun for home defense that is a little larger than what they may be able to conceal on their person.
Another common use for handguns is target shooting. This can be just for fun, or it can be used to train for self-defense. Lastly, most people do not often use handguns for hunting, other than carrying a self-defense sidearm. Some specialized handguns are large enough to hunt with, but they are certainly outside of the norm.
A general idea to know is that handgun calibers are usually larger than rifles. Some common handgun cartridges are the 9mm (.354 inches) Luger, .40 S&W, and the .45 ACP. All being fat calibers over 0.35 inches in diameter. Meanwhile, you will have to go looking a little bit to find a common rifle cartridge much bigger than .30 caliber. Still, rifle cartridges are usually much more powerful than handgun cartridges even if their caliber is smaller.
The Shotgun Curveball
Unlike handguns or rifles, shotguns do not use a caliber measurement. Since they fire a lot of smaller BBs (called shot) instead of one large bullet, they use a term called gauge. Gauge is a measurement of the diameter of the bore of the shotgun. Although it isn’t that straightforward, the number representing gauge is the number of lead balls that are the size of the bore’s diameter that it would take to make one pound of lead. For example, a 12 gauge shotgun gets its name because it would take 12 balls of lead the size of the 12 gauge’s bore (0.729 inches) to weigh one pound.
Shotguns are most commonly used for bird or waterfowl hunting since the spread of BBs makes hitting them easier (but not easy!) in the air. Shotguns are also very popular for home defense due to their shot spread making it easier to hit a target. Lighter shotguns are often used to hunt small game, and the standard 12 gauge can be outfitter to hunt big game such as whitetail too.
Most shotgun gauges available are 12 gauge and 20 gauge, and 12 gauge is by far the most popular for adults. The 20 gauge has lighter recoil and is usually used by smaller hunters, but it is still highly effective.
Small Game & Varmint Hunting Calibers
Now we can dive into rifle calibers. There is a bit more breadth in the rifle cartridge market. Nowadays, it seems like there is a purpose-made cartridge for everything. So no matter what you want to use your rifle for, someone somewhere has made a cartridge just for you.
We talked briefly about hunting small game with the .22 Long Rifle earlier. It is an extremely popular cartridge molded to many uses. However, if you want to hunt something a little larger than a squirrel or a rabbit, such as a raccoon, groundhog, or fox, you can use a more powerful cartridge like the 17 Hornet, or 22 Magnum.
This class of cartridges is really a “do it all” kind of cartridge. Like mine, your grandfather likely walked the woods with a 22 Magnum and took everything from a rabbit to a deer home with it. Nowadays, there are restrictions on how small of a cartridge you can use for deer, and 22 Magnum doesn’t usually make the cut, but it depends on your state.
Still, if you want a rifle that can be used to hunt a variety of game, something between .17 and .22 caliber is ideal. If you increase the caliber ever so slightly, you enter a more powerful class of cartridges that many people use for varmint hunting.
Cartridges like the .223 Remmington / 5.56mm NATO, 224 Valkyrie, 204 Ruger, and the .243 Winchester are all extremely popular for hunting coyotes, bobcats, and other larger varmints. There are plenty of exceptions, but in general, you will stay between .20 and .24 caliber for small game and varmint cartridges.
Big Game Hunting Calibers
Big game hunting is where there is a lot of innovation in the ammo industry. Every year, new cartridges are promising to be the next best cartridge to take down your trophy deer or elk, and everyone is eager to try it out. That leaves us with a very long list of cartridges to choose from when we are ready to buy.
This category has a variety of bullet calibers. You will see 6.5 mm (.256 inch), 7 mm (.275 inch), and .30 caliber bullets most commonly; however, dozens of cartridges fit somewhere in between all of those. In general, you could find cartridges labeled for big game anywhere between .240 and .340 caliber.
Even though these calibers may be comparable to other cartridges we talked about for small game or varmint hunting, big game cartridges are a bit bigger and much more powerful, usually being overkill for anything much smaller than a deer.
Which big game cartridge is the best for you depends on what you are hunting, how far away you want to shoot it, and a whole lot of opinion. There may not be another topic debated in the hunting world as much as which cartridge is best. There are thousands of articles about it and plenty of books. Personally, if I am hunting whitetail, I have a .308 Winchester in my hand. If I am out west, I usually carry a .300 Win Mag.
Long-Range Shooting Calibers
Long-range calibers will not be too different from big game hunting calibers. There is also plenty of overlap between the two categories. The big difference is that many people rarely shoot much over 200 yards at big game, whereas long-range shooters might warm up with 200 yards.
There is no concrete definition of what “long-range” means, but it is generally considered to be anything over 500 yards. To shoot that far, you will want a fast cartridge that has as little bullet drop as possible while it is flying. Cartridges that do this are often called “flat shooting” cartridges, and consequently become popular for big game hunters since they usually do not want to worry at all about bullet drop. One example is the now uber-popular 6.5 Creedmoor, which has about 10 inches less drop than the popular .308 Winchester at 500 yards.
In general, to shoot long range you will want a lightweight bullet that is sleek and aerodynamic. Then you want to shove it in a cartridge that has a lot of powder in it so that it flies screaming fast. You do not have to worry about energy transfer since you are likely only killing paper, so instead of big soft point bullets you might use for big game, you can use small full metal jacket bullets. This is usually what you get with match grade ammo and you can find a variety of cartridges between .25 and .35 caliber that would be perfect for long-range shooting.
Choosing The Caliber for You
Understanding the wide variety of calibers and their uses is essential for selecting the right ammunition for your specific use. Whether your firearm is for target practice, hunting, home defense, or long-range shooting, It’s important to remember that caliber alone does not determine a cartridge’s power or use. For example, the .22 Long Rifle and the .224 Valkyrie are similar in caliber size but vastly different in power and performance. Still, each caliber only fits in a small number of categories, and it can give you a good idea of what you would use a particular cartridge for.
