I'm speculating about test-firing a .22 inside my house in a residential area. In a concrete basement of course. While doing some maintenance on a few older semi-auto .22s (replacing springs, polishing ramps, etc.), it would be super handy to test fire them downstairs vs. driving across town to the range after each adjustment. Not target practice. Just post-maintenance functional checks, firing almost point blank into something that will catch everything safely while I cycle through a couple mags. I know that a phone book stops .22 rounds. But I'm picturing something a lot more durable and foolproof. Ideas? This is just another reminder to me that I desperately need to retire and move out of the city so I can step out my back door and rattle off a few rounds whenever I want to. Soooooooon... Thanks for ideas, pictures, links, etc.