"i know its so incredibly hard to believe that once or twice in the entire war sweaty, shellshocked, terrified john doe tossed a grenade randomly into the air and it landed in a foxhole with 3 guys manning an MG and they were all sent up into the air. "
I think that we have been watching too many bad war movies. A grenades damage doesn't really come from the boom, but from the multitude of tiny, nasty, sharp pieces of metal that get scattered about.