As early as 1942, Frankford Arsenal began the development of a Cal .30 armor-piercing incendiary cartridge, one that would be more effective against armored and self-sealing aircraft fuel tanks. The first experimental bullets were nothing more than AP M2 bullets with the lead point filler replaced with an incendiary mixture. These eventually evolved into a new bullet, a boattail design ,but still using the M2 hardened core and a small amount of incendiary mixture. The new cartridge was designated the T15. In 1946 it was adopted as the Cal .30 API M14.
Because of the small amount of incendiary mixture, the M14 was never very effective. In the late 1940s, an effort was made to increase the incendiary effect by reducing the core size and shape and using the space to increase the incendiary mixture to over 4 times the original amount. The new flat base bullet (T1E48) was loaded as the Cal .30 API M14A1.
20-round cartons of API were usually correctly labeled as T15, M14, and M14A1. But, it seems that Frankford Arsenal, for some reason, marked spam cans as M14, regardless of the contents. Why they did this remains a mystery.
Does anyone have FA cartons or spam cans marked differently? And does anyone have an explanation for the inconsistent can markings?