steves got it. 1903 the military adopted this round, 220gr, but the casing was changed, less neck, and a lighter bullet 150gr. was introduced. In 1906 the military adopted it.

Aww come on Ish its ok, :)

Anyway Jim actually had it right, 30 caliber 1906 is the year that it was adopted for military service. The round was actually introduced several years prior, tested, and then adopted by the military. It was used in variations of the Browning machingun and the Browning BAR, and the little known gun the M1 Garand.

it was adopted in 1906, as a take off of the .30-03, hence the rifle, Springfield M1903, or best known model the 03A3, but ya'll forgot to mention the .30-03/.30-06 was developed as an update to the .30-40 Krag

Much of the rest of the world at the turn of the century was in the process of adopting the pointed spitzer bullet: France in 1898, Germany in 1905, Russia in 1908, Britain in 1914. When it was introduced, the .30-03 was thus behind the times for this among other reasons. A new case was developed with a slightly shorter case neck to fire a higher velocity, 150-grain (9.7 g) spitzer bullet at 2,700 ft/s (820 m/s).

The M1903 Springfield rifle, introduced alongside the earlier cartridge, was quickly modified to accept the .30-06 cartridge, known as the M1906. Modifications to the rifle included shortening the barrel at its breech and recutting the chamber. This was so that the shorter ogive of the new bullet would not have to jump too far to reach the rifling. Other changes included elimination of the troublesome 'rod bayonet' of the earlier Springfield rifles.

Experience gained in World War I indicated that other nations' machineguns far outclassed American ones in terms of maximum effective range. Additionally, before the widespread employment of light mortars and artillery, long-range machinegun 'barrage' or indirect fires were considered important in U.S. infantry tactics.[3] For these reasons, in 1926, the Ordnance Corps developed the .30 M1 Ball cartridge using a 174-grain (11.3 g) bullet with a 9 degree boat tail, traveling at a reduced muzzle velocity of 2,640 ft/s (800 m/s). This bullet offered significantly greater range from machineguns and rifles alike due to its increased ballistic coefficient. Additionally, a gilding metal jacket was developed that all but eliminated the metal fouling that plagued the earlier cartridge.

Wartime surplus totaled over 2 billion rounds of ammunition. Army regulations called for training use of the oldest ammunition first. As a result, the older .30-06 ammunition was expended for training; stocks of M1 ammunition were allowed to slowly grow until all of the older ammo had been shot up. By 1936 it was discovered that the maximum range of the new M1 ammunition and its 174-grain (11.3 g), boat-tailed bullets was beyond the safety limitations of many ranges. An emergency order was made to manufacture quantities of ammunition that matched the ballistics of the older cartridge as soon as possible. A new cartridge was developed in 1938 that was essentially a duplicate of the old M1906 round, but with a gilding metal jacket and a different lead alloy, resulting in a bullet that weighed 152 grains (9.8 g) instead of 150. This cartridge, the Cartridge .30 M2 Ball, used a flat-based bullet fired at a higher muzzle velocity (2,805 ft/s) than either of its predecessors.

.30 caliber cartridge, model 1906

Adopted by US military in 1906.