Headstamp

A headstamp is the markings on the bottom of a cartridge case designed for a firearm. It usually tells who manufactured the case. If it is a civilian case it often also tells the caliber: if it is military, the year of manufacture is often added.

The headstamp is punched into the base of the cartridge during manufacture. A resource for identifying where the ammunition originated can be found at Cartridge Collectors.

Military Headstamps
Military cartridge headstamps do not usually have the caliber and cartridge name on it. The headstamp may have a 2- or 3-symbol letter, number, or alphanumeric code indicating the place of manufacture. This is usually followed by two digits indicating the last two digits of the year of manufacture. Early 20th century cartridges may have additional digits or a letter indicating the month of manufacture. The packaging usually has the manufacturer code, 2-digit year, and a lot number on it so bad or suspect batches can be removed.

Civilian Contractors

 * FCC Federal Cartridge Corporation - Anoka, Minnesota
 * RA Remington Arms - Bridgeport, Connecticut
 * US United States Cartridge Company - Lowell, Massachusetts (1867-1926).
 * W or WCC Western Cartridge Company - East Alton, Illinois
 * WRA Winchester Repeating Arms Company - New Haven, Connecticut

Commercial Cartridges
The US military used commercial cartridges for its training rifles, non-standard weapons, and shotguns. These usually had different headstamps than the military ammunition (usually their civilian one) and were shipped in commercial crates rather than military packaging.
 * ♦ Western Cartridge Company - East Alton, Illinois:
 * F Federal Cartridge Corporation - Anoka, Minnesota
 * H Winchester Repeating Arms Company - New Haven, Connecticut:
 * P, PCCo or PETERS Peters Cartridge Company - Kings Mills, Ohio:
 * REM-UMC Remington-Union Metallic Cartridge - Bridgeport, Connecticut
 * U Remington Arms - Bridgeport, Connecticut: