How to Understand Ammo Headstamps

Home / How to Understand Ammo Headstamps

Ammo headstamps are the markings on the base of a cartridge case or shell casing. These markings provide valuable information about the ammunition, including its caliber, manufacturer, and sometimes even the year of production. Understanding headstamps is important for shooters, collectors, and anyone who wants to identify the type of ammunition they’re dealing with. Here’s what you can typically learn from ammo headstamps:

What you Can Learn From Ammo Headstamps

Caliber or Gauge:

The most basic information provided by a headstamp is the caliber or gauge of the ammunition. This is usually represented by a number followed by a unit of measurement (e.g., “9mm,” “45 ACP,” “12 GA” for 9mm Luger, .45 ACP, and 12-gauge shotgun, respectively).


The headstamp often includes the name or initials of the ammunition manufacturer. This helps users identify the source of the ammunition. For example, “WIN” stands for Winchester, “PMC” for Precision Made Cartridges, and “Federal” for Federal Ammunition.

Country of Origin:

Some headstamps indicate the country where the ammunition was manufactured. This can be important for collectors or those interested in the origins of their ammunition. For instance, “USA” indicates the United States, “RUAG” represents Swiss-made ammunition, and “TULA” stands for Tula Cartridge Works in Russia.

NATO Symbol:

Military ammunition may feature NATO symbols, which indicate compliance with NATO standards for ammunition. This often includes a circle with a cross in the center. It signifies the ammunition meets NATO specifications.

Lot Numbers and Codes:

Manufacturers may include lot numbers or production codes on the headstamp, which are used for quality control and traceability. These numbers or codes are typically not standardized and may vary between manufacturers.

Year of Production:

Some headstamps include the year it was manufactured, usually in a two-digit format. This helps determine the age of the ammunition. For example, “21” could represent the year 2021.

Symbols and Special Markings: Special symbols or markings can offer specific information. For example, a “+” sign next to the caliber might indicate higher pressure loads, while a “G” may denote tracer rounds.

Proof Marks:

In some countries, proof marks or stamps indicate the ammunition has undergone testing and meets safety standards.

Metric vs. Imperial Units:

Depending on the manufacturer and country of origin, you may find headstamps using metric units (e.g., “9mm”) or imperial units (e.g., “.45 ACP”). This can be important for ensuring you select the correct ammunition for your firearm.

While headstamps often follow some conventions, they can also vary significantly based on the manufacturer’s preferences and country-specific regulations. So, it’s important to consult reliable references or seek expert advice if you’re unsure about any markings on your ammunition.

Understanding ammo headstamps can enhance safety, help identify collectible ammunition, and ensure you’re using the correct cartridges for your firearm. Always exercise caution when handling and using ammunition and follow proper safety procedures.