Anyone ever make one of these? I want to make a rimfire one and just wondering how thick the steel needs to be on the targets. I saw this kit on eBay and it got me thinking, http://www.ebay.com/itm/Do-It-Yours...649?pt=LH_DefaultDomain_0&hash=item460429df01 . I have plenty of steel, I own a large machine shop. Would be nice to through 1 or more of these things together.