An incomplete history of the Cal. .30 TRACER. Please feel free to fill in the blanks.
The first Cal. .30 Tracer adopted by the United States was the M1917. Identified by a blackened case, the M1917 was loaded with a 150 grain CN bullet. Close examination will reveal a small ring about 1/16" from the tip of the bullet. The purpose of the ring is unknown.
During the early 1920s several experimental tracer cartridges were tested. None were adopted and the M1917 remained the standard until 1923. The M1923 was a short lived tracer intended for aircraft use. It also had the blackened case and a GM bullet.
The M1924 was loaded with two colors of trace mixture - red and green. Using blackened cases with a GM bullet, the cartridges are most often identified by the box label but primer seal color can sometimes, but not always, be used.
The M1924 was replaced in 1925 by the new Cal. .30 M1 Tracer. The first cartridges had blackened cases and a GM bullet. Primer seal colors were used for a few years only. In 1930 the blackened cases was replaced with plain brass, the green tracer was discontinued and the red tip was added for identification.
In 1942 a tracer with a short burn time was adopted. Designated the M2 it was identified by a white tip, a second cannelure, or both. That identification was soon replaced by a red tip and the second cannelure. Also developed in 1942 was a special experimental dim tracer for aircraft use identified by an orange tip and designated the T10
In 1945 the T10 became the M25 and continued as the standard throughout the service life of the Cal. .30.