How To Identify Ammunition

For the uninitiated, it can sometimes be confusing trying to identify different types of ammunition. There are a plethora of calibers and cartridges in existence. Many using the same caliber sizes but are of different designs. So how do we know what to use? For starters, let’s take a look at the firearm. The majority of firearms will have the specific cartridge type stamped or engraved on the barrel or receiver. Before choosing which ammunition to use, you should always check these to confirm what your weapon is chambered for. This will determine what you need. So how do we make sure the ammunition is correct?

You should never risk judging ammunition solely on appearance as mistaken identity could lead to weapon failure or serious injury or death to the operator or bystanders. Many casings will include information about the cartridge on the headstamp; “a marking on the head of a cartridge case.” (Vigil, 2021, p. 1) The information on the headstamp will usually include the type of cartridge. Sometimes abbreviations are used to shorten the amount of information included for space constraints; for instance, the 45 automatic may be shortened to 45 auto or 45 ACP. Other information can include the maker of the ammo, date manufactured, and/or location manufactured; indicated either by letters, numbers, or symbols. (Vigil, 2021, p. 1) Ammunition created by or for the military may have different markings from what’s made for the civilian market. What if we don’t understand the headstamp markings? 

Ammunition that doesn’t include the cartridge type on the headstamp but instead includes symbols or other identifiers can be difficult to identify without a reference. Some good resources for identifying these are the International Ammunition Association, Inc., Association of Firearm and Tool Mark Examiners, and the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. It is always better to wait until you’ve identified the cartridge before you use it. Take for instance the 5.56x45mm NATO and the .223 Remington. These two rounds appear identical and each will chamber in the other, but “it is not safe to shoot ‘5.56,’ ‘5.56 NATO,’ or ‘5.56x45mm’ ammunition in a barrel marked as being chambered in 223 Remington for a number of reasons. The main reason being that a barrel marked as chambered in 223 Remington will have a shorter throat into the rifling than a ‘5.56’ barrel which may cause increased pressure if the ‘5.56’ ammunition is fired in it.” However, “It is safe to shoot 223 Remington ammunition in a 5.56 military specification chamber.” (SAAMI, 2023) So what should you do if you get a mixed bag including each of these cartridges and not all include the type on the headstamp? 

In the above instance, depending on which your firearm is chambered for, it could be hazardous to use the wrong one. You could use the afore mentioned resources to identify the symbols or monikers to confirm correct type. But if all research fails, it would be best to err on the side of caution and treat all the unidentified rounds as 5.56x45mm NATO, as it would be the more hazardous round to use and treat them accordingly. Overall, always be cautious and identify the ammunition before use. 

1. SAAMI. Sporting Arms and Ammunition Manufacturers’ Institute, Inc., FAQS. 2023.

2. Vigil, Frank. “Headstamps.” 2021. Sonoran Desert Institute. Pp. 1.