what you could do is make a mold of one. you would have tio make it without the pin of course the cut a hole in the middle
and stick and m-80 in that beotch.
runn arround like an idiot scream firee in the hole then throw next to someones house.
M-80s are too weak. Get some real gunpowder, or better yet, C4 if you have a demo license (which I don't, but meh)
Other than that, your best bet would be to buy a surplus one and make a mold off it or just craft it out of clay.
Deactivated grenades would work extremely well in both scale and resemblance. The M9 HE-DP's are about 3.5", not much bigger than a real one. Just wouldn't want to talk them out in public or anything. :rolleyes
Yes the halo grenades are fictional, but the type of grenade (Fragmentation A.K.A. Frag) are very real.
Yeah for the safety of your props (in response to the guy who said be careful) just put blaze orange tape or paint on it somewhere easily visiable and you should be okay as long as you aren't hucking them at people or threatening people.
Anyhow, great idea give it a try, i personaly would like to sculpt a spike grenade
sometime i will,