Originally Posted by BMCM

Part of what keeps the slide velocity under control is drag pressure from the ammo stack in the magazine. As the guns get smaller and shorter this becomes especially critical since the shorter, lighter slides on the sub-compacts cycle so much faster. It become quite a bit more of an engineering challenge to solve, keeping the slide slow enough that it does not outrun the magazine... and do this consistently. Allow or cause the slide to cycle too quickly and it closes on an empty chamber. This having run right past the ammo stack because it cycles faster than the magazine spring can lift and present the next round before the breechface.

There is a balance between three springs that keeps slide velocity in check; The mainspring controls slide velocity at the beginning of the firing cycle as the rearward slide travel cocks the hammer when the recoil spring is at it's weakest near installed length, The magazine adds drag through the ammo stack to slow the slide down throughout the cycle. And the recoil spring which would be more correctly termed the 'return to battery spring' brakes the slide to a halt and returns to battery stripping the next round off the ammo stack on the way.

Mess with any of those springs... allow then to become weak ... install extra power springs for no reason... replace mainspring with lighter spring to lessen DA trigger. (poor man's trigger job) and you invite problems.

Your CS9 is behaving exactly as it should. I second 18DAI's advice... Don't try fixin' whut ain't broke

I thought this might help you understand whats going on under the hood and why it's behaving as designed.

Cheers
Bill