Speed of sound is about 1159 FPS. Remington and Winchester subsonics go 1050FPS and CCI SV go 1070 FPS. One of my Marlin 60's does not like the truncated cones of the Winchester subsonics. The Rugers and other Marlins semi's shot them all fine.
Those are the cartridges I shoot,I tried the Quiet Round ,rifle shot did not eject.
I have found going much slower, the accuracy diminishes! Cliff