How do you mill an empty hand grenade?

Inert hand grenades can be bought legally. I have no explosives, no detonator, even the grenade itself is heavily corroded. I don't really see any similarity between an inert grenade (which in fact qualifies as an antique/collector's item) and a .50 caliber MG (supposing you mean the machine gun, not just an inert .50 cal. round).

I guess it could still be refilled if somebody wanted to. I think you could make a much more effective device with a stick of dynamite placed in a metal can filled with scrap iron, though.

I know collectors who own literally hundreds of inert rounds, grenades and shells. If the BATFA arrest me for that lousy empty Mills bomb I wonder what they're going to do to all those collectors?