Cool, where can I get one of those? It would go good with my 81mm mortar, and 105 howitzer. Talk about a great 4th of July...
[Sidebar: And no you richard heads reading this, I don't have an 81mm mortar]
5.56mm
Why not? Ammo is kind of expensive I guess, since you have to pay the "Destructive Device" tax on each round. :)