SDC
Member
This is something that a Russian designer named Baryshev has worked out; a CONTROLLABLE full-auto full-power rifle that operates as a delayed blow-back. He has made these in calibres from 5.45 to 30mm grenade, and the link shows the 7.62x39, 7.62x54, and 30mm versions being fired, with a remarkable lack of recoil. Here's a shot of the bolt design he submitted with his patent application.
http://www.youtube.com/watch?v=ugcLyrSdT1s&feature=g-vrec&context=G251221fRVAAAAAAAABA
http://www.youtube.com/watch?v=ugcLyrSdT1s&feature=g-vrec&context=G251221fRVAAAAAAAABA