Ammo Headstamps Explained: Reading the Bottom of a Cartridge
May 19, 2026 · AmmoBin.com
The stamped markings on the base of a cartridge — the headstamp — tell you who made it and often the caliber. Here's how to read them.
What's on a headstamp
A headstamp typically shows the manufacturer (a name or code) and the caliber; military ammo often adds a date/lot and a NATO cross (a circled plus) indicating it meets NATO spec. Commercial ammo usually spells out the caliber (e.g. '9mm Luger').
Why it's useful
The headstamp confirms what you're loading — handy when boxes get mixed, when sorting range brass for reloading, or when identifying surplus. It can also flag a NATO/military round (e.g. 5.56 NATO vs .223) which matters for pressure.
Pair this with knowing your primer type (Boxer vs Berdan) when sorting brass. Compare live 5.56 prices.
Frequently asked questions
What does a headstamp tell you?
The maker and usually the caliber; military rounds often add a date and a NATO cross. It's how you identify and sort cartridges.
What is the NATO cross on a headstamp?
A circled cross indicates the round meets NATO specification — common on 5.56 NATO and 7.62 NATO military ammo.
Compare live prices