Will explosives be at all effective as zombie-killing weapons? If you chuck a grenade into a group of zombies, it might blow off a leg or two, but will it actually do anything but slow them down? Same goes for mines, C4 and - arguably - grenade launchers and RPG's.
Sounds realistic. That said, shrapnel can still hit the head, so...
True. But if you don't mind, I'll just cite what Max Brooks' The Zombie Survival Guide has to say about explosives:
"Question: What could be better than hurling a hand grenade at a mass of approaching zombies? Answer: almost anything. Anti-personnel explosives kill mainly by shrapnel, metal shards tearing through vital organs. As this will not affect zombies, and the chance of shrapnel penetrating the skull is slim, grenades, bombs, and other explosive tools are inefficient weapons."
Shrapnel is designed to pierce all the important fleshy bits in the torso and abdomen, not go through bone. That said, the books goes on to say:
"These devices should not be completely discounted, though. For blasting doors, creating instant barricades, or even scattering zombie mobs, nothing works better than a jar of gunpowder."
Anyway, my point is basically that I hope you'll make explosives as realistic as possible.