Thanks for the suggestions.....
Recoil springs on short-barrel pistols like the CS9 have to work very hard indeed. I have the same issue with my CZ RAMI BD even with the dual-spring I need to replace the outer spring every 500-1000 and complete set including inner every 3rd change. When the return to battery starts to 'ker-chunk' it's already past due.
I found Wolff caries a variety of recoil spring weights 14# to 18# for the 3913 series. Any recommendations?
Because I typically shoot a bit hotter practice ammo (usually S&B 115 or 124 depending on gun) closer in PF to my SD ammo, I would think a heavier 16-18# spring to be on the safe side??
Numrich Arms is out-of-stock on the CS9 recoil springs, but I got on their 'back-in-stock' email notification list.
Their other parts listed for these guns seems pretty comprehensive.
I've never owned a 3rd-Gen Smith until now, but most of what I've heard is positive. Looking forward to it.