Those are mil spec primers. The main difference is that the cups are made from thicker/harder material. There may be some other small differences in construction but hey are designed to prevent slam fires in military guns. Mostly the full auto ones. You can imagine the violence that a round is subjected to as it makes it's way into the chamber of say, a 240SAW. Some military guys use them exclusively but in the civilian world I don't believe they are unnecessary. I think the priming composition is the same as a magnum civilian primer. Which would make sense if you consider the large range of conditions that they must operate in.
Seems they would also be useful in rifles with floating firing pins, like alot of military rifles. Mostly i use them for better accuracy with W748 in 308 (bolt/lever/semi). Similarly, use Rem 7 1/2 with W748 in 223.