The thing is that gun wouldn't be acquired legally and that "facility" is not one open to a third of the country ! ( one third of Americans own at least one gun ). I'd also suspect the choice of weapon available would not be from as wide a range as you can get in a US gunshop and similarly you wouldn't be able to get limitless supplies of ammunition.
America - the place where its not thought odd to want to own a fully armed helicopter gunship...............
Exactly - you make all those gun illegal. Give them a 3 months amnesty period to hand in their guns . Then if they do not, minimum 5 years sentence. Simple.
You pays your money, you make your choice...