I had to make a rotating sear that held the bolt in the open position. Where such a sear needed to be, the magazine well was. So the sear had to be made to work around the mag. PITA, and it brought no more money than the (far simpler to modify) Tec-9's. 3 welds, and a bit of grinding had the Tec-9's firing full-auto, from the open bolt. Some of them required a bit of modification to the extractor, or the bolt would not always slam shut on a rd.