I'm wondering about the legality of this. I guess at issue is the phrase "readily convertible." It would be pretty easy to make it idiot-proof as far as making it impossible to convert back... but I know that doesn't mean anything to the ATF tech branch. What I was thinking was, weld blank firing adapter into the barrel, weld a bushing or something else into the chamber to keep loaded rounds from chambering, weld the barrel to the front trunion, and weld the front trunion to the reciever. The muster day re-enactment at camp Mabry kind of gave me the bug bite for this. Some guys there had some kind of blank-firing full-auto ww2 sub guns that they used in the re-enactment. So... anyone tried this? Anyone ask the ATF's opinion of this, yet?