On the other hand, banning toy guns altogether is a bit much, and likely to be counterproductive.
I would dare to suggest that, among little boys, some sort of gaming involving guns (battle, cops, cowboys, etc.) is absolutely inevitable. Some kids might be satisfied with a "gun" cut from cardboard, but others will be indulged by parents or grandparents with either a realistic toy bought out of state, something carved by grandpa and painted to look real, or maybe an unloaded or defective real gun. It could happen, and the same mistake will recur.
I was the first kid on the block to play ARMY with a real gun. My uncle gave me a WWII Japanese rifle with the firing pin removed. I thought it was real neat to have such a realistic toy to play with and I don't remember any of the neighborhood parents or kid complaining about it.