Bat, you are most correct sir and I built it. It's a DPMS slickside upper, a CNC Enterprises dedicated greasegun mag lower, Olympic Arms bolt and barrel, a WW2 Cutts compensator from Belgium and Thompson wood. It took forever to find a guy to machine the fins into the bbl. My buddy used his mini lathe to drill and tap the Cutts so that it screwed onto the bbl. The bbl threads are inside of the Cutts. I had a local custom moulding wood shop router the buttstock for the buffer tube extension. I inlet the grip onto the lower and built the gripmount for the vertical grip. There also was a bunch of tinkering with buffer springs as the extension is shorter than normal. There is a shroud on the bbl nut now. The drum is from an airsoft gun with the guts removed and a cutdown greasegun mag installed. Overall, this build took a few years.