User blog comment:Drayco90/James "Jim" Raynor vs. Master Chief/@comment-3528601-20110606001750/@comment-422690-20110606004942

Considering that a mesh made from string made from spider silk has been shown to stop bullets, I think it's safe to assume that MJOLNIR armor is made of s similar synthetic substance to be able to take as much abuse as the people claim and still be light enough to move in.