.50cal "∟C43" double cannelure

Why is there an extra cannelure in 50cal incendiaries? What’s the purpose? Ammo illustrations are from 1986 US Department of the Army ammunition handbook.


Ray–I’m sure identification is part of it, but someplace I heard that the extra cannulure is to help lock in the incendiary capsule.

Not all the Cal .50 Incendiary bullets had the internal steel sleeve. The sleeve was to strengthen the jacket, not to act as a container for the mixture. Those that had the sleeve usually had two cannelures. The one Vlad pictured is probably an M1. I’m sure the extra cannelure helped to hold the sleeve in place but the rear cannelure and lead slug were probably sufficient to do the job. Note that Cal .30 Incendiary also has a sleeve but has only one cannelure. And, many other bullets that had two cannelures usually had the 2nd cannelure for identification only.

So, we’re probably both right.