How to Read an Ammo Box

How to Read an Ammo Box

Ever experienced "information overload" when ammo shopping? How do you find the right caliber ammunition for your firearm, what do the numbers on the box mean, and how do you decide between ammo brands?

Find Your Caliber

First off, it is critical to recognize what caliber ammunition goes into the gun you want ammo for. If you feed your gun the wrong "gun food", the results can be disastrous. How do you find the caliber of ammunition that your gun takes? It is always marked on the barrel or frame of the firearm. This is called a "rollmark" and it is critical that you identify what your firearm caliber is and only use the ammunition that chamber is designed for.

The caliber of the firearm is always marked on the barrel or frame - this Ruger American Magnum Rifle is chambered in 300 Winchester Magnum.

Once you know the caliber to look for, head online or to your local gun shop and locate the ammo section. If they are organized you'll be able to locate your caliber ammo by size (just watch out for the metric sizes - 9mm could end up in "9" or somewhere around 0.355") and by gun type.

What Might Be On The Box

There are a lot of options that will show up on a box of ammo. Some rounds are full metal jacket, meaning the lead bullet is covered in a harder metal like copper - typically for the purposes of higher speed and easier feeding into the chamber. Some rounds are hollow point or jacketed hollow point.

"How does it work? Put simply, hollow points expand on impact. The design of JHP rounds means that the bullet typically turns into a mushroom shape when it hits its target, resulting in a larger wound channel than would be made by an equivalent full metal jacket (FMJ) round." - Real Clear Defense

Some rounds are "+P" or "+P+" - only use these overpressure rounds if your gun's chamber is rated for it. Frangible rounds will break apart on impact, which makes it great to shoot at steel. In addition to cartridge design, there's bullet weight, case material, intended speed (subsonic, supersonic)...

All these varieties of cartridges are designed for a specific purpose. A little research will guide you in the direction of cartridge characteristics that will work best for you.  Obviously, there are a lot of options. What ammo to buy depends on your application and the firearm(s) you plan to use. 

Handgun Ammo

A sample 9mm ammo box

This box of handgun ammo has the caliber ("9mm Luger"), the bullet weight ("100 Gr"), and the fact that it is frangible centerfire ammo. 

Are you a shooter new to handguns? If you want to learn more about pistols and revolvers, check out my Handy Guide to Handguns.

Rifle Ammo

A sample .300 Win Mag rifle ammo box

This box of rifle ammo has the caliber ("300 Win. Magnum"), the bullet weight ("180 Grain") and the fact that it is "soft point", which is meant for hunting big game.

Curious about different types of rifles and what ammo they take? You can read more about the most common rifle types, including bolt action rifles like the .300 Win Mag hunting rifle, in my Guide to Rifles.

Shotgun Ammo

A sample 20 gauge shotgun ammo box

This box of shotgun ammo has the gauge ("20"), the shell length ("3 in" - only fireable in a chamber sized for 3 inches or longer), the shot weight ("1 5/16 oz"), and shot size ("6 shot"). The label also tells me that it is copper plated, which should help with penetrating through layers of feathers and skin in turkey hunting. The muzzle velocity is also included on the label, which could be helpful if comparing two very similar loads - faster is better for turkey hunting with this type of ammo.


There is a LOT to think about when buying ammo, but the info on the label is just there to help you choose what will work best for you. The most important thing to do is match the caliber to the rollmark on your firearm. Beyond that, what you choose is up to you and your application. If you have any questions, feel free to contact me, as always!

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