Are you familiar with the 45 cal grease gun? It had a 4 lb bolt which completely countered the recoil.
I never fired one but I saw a trainng film for them. The Instructor put the heavy wire stock against his chin and fired long bursts with no apparent jarring to his head.
They had a 50 lb steel plate with a sort of hoop on one side which fit over an upright steel pole. First the Instructor fired a 3006 M1 round at it. The plate moved about 180 d. Then he hit it with a 45 round from the grease gun.
The plate spun around the pole about 3 times. Next he fired a burst at the plate. It spun like a top.
No kick on the shoulder end but awesome on the impact end.