The .30-06 Springfield (Metric calibre of 7.62 x 63 mm) was a rifle round used in a wide assortment of American weaponry. In practice, the .30-06 Springfield came in two forms, the M1 and the M2 Cartridges, each with their own specifications. Both had an overall length of 85 mm and rim diameter of 11.9 mm. However, the heavier 174.5 grain M1 bullet had a muzzle velocity of 807 meters per second compared to the 152 grain M2 bullet's 855 meters per second.
For storage and transportation, the M2 cartridge used with the M1 Garand was stored in eight round en bloc clips kept in cloth bandoleers capable of holding six clips. Both cartridges were also stored using the .30 Caliber M1 Ammunition Can when being packaged for machine gunners. Inside the ammunition can, the rounds themselves were organized into canvas or disappearing metal link belts also used for aircraft.
- Cartridge, Ball, Caliber .30, M1: 9˚ taper "boat-tail" design with a bullet weight of 174.5 grains. Bullet core changed to 7 parts Lead to 1 part Antimony.
- Cartridge, Ball, Caliber .30, M2: Design with bullet weight of 152 grains. Bullet core changed to entirely reclaimed lead. Meant to be a less powerful version of the M1.
- Cartridge, Caliber .30, Armor Piercing, M2: Armor piercing round used against light vehicles or light shelters. Features a black-tip for identification.
- Cartridge, Caliber .30, Tracer, M1: Tracer round used for signaling or observing rounds fired. Features a red tip for identification.
- Cartridge, Caliber .30, Tracer, M2: Tracer round used for signaling or observing rounds fired. Features a red tip for identification.
- Cartridge, Dummy, Caliber .30, M40: Training round
- M1 Rifle Grenade Cartridge Case with no bullet designed to fire rifle grenades.
The .30-06 Springfield began its development in 1903 with the creation of the relatively slow 220 grain .30-03 Springfield cartridge that was promptly replaced with the design of the 150 grain .30-06 spitzer (sharp nosed) bullet so as to keep up with the performance of contemporary cartridges. Even with this change, World War I military experienced demonstrated that the .30-06 was still an unsatisfactory cartridge, with a far shorter effective range than opposing nations' cartridges.
As a result, work began on the M1 Cartridge in 1925, standardized for use that same year. The chief difference between the earlier .30-06 cartridge and the new M1 was that the M1 was given a 9˚ taper "boat-tail" design at its end to help reduce the drag that plagued the earlier round. This made the round overall more powerful at longer ranges and helped the heavier 174.5 grain bullet maintain a good performance. However, at the time of the M1's standardization, the United States already possessed a stockpile of some 2 billion rounds of older .30-06 ammunition, meaning that the new M1 ammunition did not start appearing until 1936 when the original ammunition had been used.
Though incredibly accurate, the M1 was deemed too powerful for the needs of the American government, and thus the M2 Cartridge was created in 1940 with some of the traits of the original cartridge including a smaller 152 grain bullet. To save on Antimony, the core of the M2 was replaced with reclaimed lead. One notable example of the M1's power and accuracy came later during the Solomon Islands campaign in 1942 where the US Marine Corps kept stocks of M1 ammunition for use by snipers. By the time World War II had reached the United States, the .30-06 Cartridge in all its forms became one of the most common ammunition types employed by the American military in a variety of forms, from infantry weapons such as the famous M1 Garand or M1918 BAR to the machine guns in aircraft such as the Bell P-39 Airacobra or Boeing B-17 Flying Fortress.