Here's what I came up with. Not testfired yet -
Had to have access to the top screw that holds the G3 stock to the backplate, which made it more complicated. A G3 buffer spring, about 1" long, goes in the back of the tube. It's a VERY HEAVY DUTY spring. Turned a 'plug' to go if front of it
The steps on the 'buffer plug' are clearance cuts for the feed stud plate, and feed lever (in the TC). The back of the bolt stem centers on the buffer plug
The short sections of recoil spring are only for illustration. Actual springs are much longer. There's a slot with a screw in the bottom, to secure the buffer plug & keep it aligned. I used a C-clamp to partially compress the buffer spring, for assy, so it's already under pressure.
Had I anticapted the actual energy of the cartridge, it would have been designed differently. And it would look neater, instead of bent back in shape and re-done with welds on top of welds. Next one should be better; maybe a rotating bolt with a tight gas system and super-light BC. Straight blowback doesn't need the gas assist. These MG47's are addictive beyond description