The letters and numbers stamped into the face of a cartridge case or shotgun shell to identify its caliber or gauge.
Virtually all cartridge cases have headstamps on their bases.The headstamp is a series of letters,numbers,symbols,and/or trade names.They are either imprinted or embossed on a cartridge case head for identification purposes.Civilian cartridges are usually marked with the initials or code of the manufacturer,as well as the caliber.Military cartridges are usually marked with the manufacturers initials or code plus the last two numerals of the year of manufacture.The caliber may be designated as well.American military match ammunition has the word "match" or the letters "NM' (National Match) imprinted on it.Ammunition meeting NATO specification carries the NATO symbol which is a cross within a circle.
Headstamp are not necessarily reliable indicators of the caliber of the particular cartridge case or the manufacturer because a cartridge case may have been reformed to another caliber.Thus a .308 cartridge case may have necked down to a .243 cartridge.Commercial concerns that buy large quantities of ammunition may have their name stamped on the cartridge cases rather than the designation of the actual manufacturer.
Ammunition manufactured by Russia and Japan during world war II and some 7.62 X 39 mm ammunition manufactured by the U.S. government during the Vietnam war do not have headstamps.Occasionally,a cartridge case may be seen with a surcharge.These are markings added to the base of the cartridge after the original headstamp has been formed.They are not necessarily applied in the plant that performs the original headstamp operation on the cartridge case and they may indicate that the cartridge has been reloaded.
Handgun Ammunition with a headstamps reading +P or +P+ indicates that the ammunition is loaded to higher pressures than normal for the particular caliber cartridge.
Handgun - by the way is a gun designed for use by one hand,chiefly either a pistol or revolver.The term handgun was first used in the year 1388.Firearms have been around since about the year 1245 - 1250.