^ Ah! I breathe easier now, but how about zoning codes? (Just trying to keep you out of trouble.)
My own live-firing range opportunities are somewhat limited, so I use various non-powder arms around the house for practice, with appropriate backstops and safety precautions. I like your idea of an old filing cabinet. I've got a Beeman Pellet trap, but it won't handle much power --my Feiwerkbau .177 pellet rifle dented it up a little, so I put a plate of aluminum into it along with some carpeting to muffle the impact noise.
I've got Airsoft Clones for many of my real handguns, and that keeps me reasonably happy.
One thing I got recently is a propane-powered clone of my 1911, but believe it or not it's too noisy for an apartment --should be fine for a detached dwelling. I have to wait until my neighbors are gone to use it, but it sure is fun. It has the heft of a real gun, and actually recoils from the slide coming back.
Similar to my CO2-powered PPK clone in terms of fun, but the PPK is quieter.