Dating cartridge headstamps
The Browning M2 machine gun was the most widely used weapon on the American bomber and fighter planes of WWII.
Due to the high demand of ammunition for this gun, many companies began producing the .50 caliber round to keep the supply available.
Up until 1945, all Japanese Army ammunition was bereft of markings.
Only the Japanese Navy used headstamps on its ammunition.
Other information can include case material, propellant type, bullet type, that is, tracer, armour-piercing, and so on (Figure 2.18).
The mark can consist of numbers, letters, trademarks, figures or any combination of these. They can be in any language, numbering system or can relate to any calendar.
From these impressions, one can, depending on the type of ammunition and its origin, determine the manufacturer, calibre, type, date of manufacture, batch number, case material, and so on.
This information only relates, however, to the cartridge case and does not necessarily indicate that the other components, that is, primer, bullet and propel-lant, were of the same origin as the case.
Many cartridge case manufacturers sell their cases to small companies who load them to their own specifications, and it is not unusual to find that the bullet, cartridge case, propellant and primer all have different sources.
LM = Lowell Ordnance Plant - Lowell, Massachusetts. Headstamp images are approximately 2.3x actual size.