We have loads of BB guns, biodegradable ammo, targets, face protection masks. We live next to a big wood, with dell areas perfect for playing safely without harming anyone or anything, as there is clear visibility....I do not stay and play, I wander off with the dogs...I know the temptation for dh and I to shoot one another in the bum, would be too big. The guns are bright orange in a range of styles, black replicas are illegal, and the boys only use them when with dad.
When they have mates round an essential part of play is getting the BB guns out. They also have metal catapults, hand made catapults and their own hand made bows and arrows, which are a testament to dh skills at teaching them woodland crafts. Oh and nerf guns for playing inside or in the garden when dads not home.
I would much rather they are in the garden doing target practice, or running round the woods, than blasting off the heads of realistic animations on ps3 war games.
All three are gentle, animal loving boys, who would rescue a fly rather than hurt it, and although we live in an area big on hunting, fishing and shooting, they only partake in catching the occasional minnow..
In conclusion, if you have a big garden or private woodland to play in, then I would say let him get it out of his system, under adult supervision, and if doing owt but target practice, wear face protection. Should you hate the idea, then you make the rules and your beliefs come first.