Made this recently. As with the stun gun, I decided that I wanted a non functioning but solid replica. I filled the whole thing with milliput before putting the back panel on. It is indeed, solid and quite weighty too.
I doubt it! As it was, I possibly overdid the weight. If I'd filled it with steel bearings, I'd be able to knock nails in with it!
Mind you, I'm assuming milliput is relatively cheap everywhere, I'm not all that far from where they make it.