i am curious about this idea. there are probably a crap ton of county or city codes youd have to get some sort of approval to get around, but what if you had a decent sized yard and buried a steel 8 ft diameter tube or something? ventilation is a key problem, but i am sure experienced people could figure that out. i wonder realistically how cheap you could do it. anyone have any ideas? it would just be a pistol range/22 range.