In 1906 the U.S. adopted a CN jacketed flat based 150 grain pointed bullet for its Cal. .30 service cartridge, giving birth to the Cal. .30 Model 1906. World War I demonstrated the need for a cartridge with a heavier bullet and longer range for machine gun use, but one that could still be used in the M1903 Springfield rifle. After several years of testing, a new 173 grain GM jacketed boat tailed bullet was finally perfected and in 1926 the Cal. .30 M1 cartridge was adopted.
At this time there were still over two billion of the war time M1906 cartridges on hand. The policy was to use the oldest ammunition first, reserving the new M1 for possible war use. Service, Militia, and Civilian shooters anxiously awaited the day when they would be issued the M1 for use. That day finally arrived in the mid 1930s but with it came some un-welcomed trouble. Not only did the new ammunition kick more, it shot beyond the safety areas of many of the existing rifle ranges.
The first could have been resolved with a simple order - “Complaining about recoil is prohibited”. But the safety issue could not be ignored. The National Guard asked the Ordnance Department to manufacture some reduced power ammunition, more like the original M1906, that could be used on the ranges. The new cartridge was very similar to the M1906, except it had a stannic stained GM jacketed 150 grain bullet so it could be distinguished from the M1. Nine lots were manufactured in 1937 and 12 lots in early 1938. Cartons of the new ammunition were labeled as Caliber .30 M1906. In late 1938 the M1906 designation was dropped and the cartridge was standardized as the Cal. .30 M2.
The M2 continued to be loaded with the stannic stained bullet until the last of the M1 was manufactured in 1941. At that time the stannic stain was discontinued and the well known and recognized GM jacketed M2 bullet became standard.