Initially, when CCI first cam out with their CCI Quiet ammunition, the box and advertised velocity had the bullets coming out of the muzzle at 710 FPS. The ONLY way I could get a Ruger 10/22 to fully function with those rounds was to employ a Volquartsen
"Firefly" bolt. This bolt weighs less than half of what the steel 10/22 bolt weighs. Changing springs, etc. , is a waste of time that's better spent shooting rather than changing parts. It's much easier to catch a fart in a bottle:
CCI did jump the velocities of the Quiets to 735 FPS, but still, some semi-autos didn't get the memo and were still stubborn concerning cooperation, so then, the 835 FPS Quiet ammunition hit dealers shelves, and things got better, but not the BEST, so we now have another CCI Quiet offering with a box velocity of 1020 FPS and all firearms seem to be happy, happy with those.
710 FPS
735 FPS
835 FPS