I just learned from a thread on rimfire central how my 1951 semi auto beehive Rem550-1 cycles with CB shorts.
It has a sliding half chamber that, for a time, puts the blowback energy all in the slide acceleration and none into extraction friction.
And I messed around with springs trying to get later models, like the Rem 552 to do that. No spring can be light enough. It will jam from too much spring... overlaps with will not feed from too little spring
