Congrats on the CS9.
Stainless or carbon slide? Single (left) side safety/decocker lever or ambi? Plastic or steel Novak Low Mount 3-dot sights?
The earlier CS guns had single side safety/decocker levers & plastic sights.
I bought an older production stainless (when the stainless model was first released) CS45 and a later production CS9.
I've shot the dickens out of the CS45 (having had it longer), but i actually like my CS9 better. Just enough smaller that it fits my hand as if made for it.
I held off on ordering a CS9 because of how well I liked my 3913. It wasn't until I borrowed a CS9 from another instructor a couple of times that I realized how well it handled and fired compared against my favored 3913.
The 3913 is a bit heavier, and has more muzzle-forward heft ... while the CS9's weight "sits back" more in my hand.
It has a lively balance, so to speak.
While the felt recoil has a bit more snap to it than the 3913 using the same loads (I've used standard pressure, +P & +P+ loads, all issued, in mine), the faster cycling and more abrupt 'snap" seem to make come back on-target even faster than my 3913.
The shorter stirrup and hammer spring makes for a little bit different trigger pull. Probably perceived differently by different folks, so only you can decide.
The factory tells its LE armorers to replace the recoil & mag springs in the same service use/time interval as the larger 3rd gens, meaning either every 5 years or every 5K rounds fired ... but I tend to be a little more conservative than that with my own CS9/45's. I try to replace them somewhere around 800-1200+ rounds, if only because it seems like those shorter, flat-wound recoil springs are working harder in the littler, harder recoiling CS guns. Just my druthers. I order them a dozen each at a time to save on shipping.
The CS9's 7-rd mag uses the same mag spring, follower, buttplate catch & butt plate as the 3913/variants 8-rd mags (same mag body as the earlier 7-rd "original" 3913TSW, although that older TSW used a different butt plate, made to conform to the cutaway grip profile at the bottom of the grip). I replace the mag springs less often than the recoil springs, closer to the regular factory recommendation, and they seem to run fine. I use the 8-rd 3913 mags for range use (they protrude below the grip frame) and occasionally as a carry spare.
Make sure the frame rails, being aluminum, are sufficiently lubed. It's suggested that armorers apply 1-2 drops on each frame rail - tops & sides - (can you see them still being a little "wet", a bit shiny, with lube when you field-strip the gun for cleaning?) ... a drop rubbed around the exterior of the barrel, especially at the muzzle where it rides in the slide's "bushing surface" ... a drop at the front of the barrel hood, where it meets the front of the ejection port when the slide is in battery ... a drop around the guide rod (what's left on your fingertip after rubbing it around the barrel ought to be enough) ... and a small drop on each side of the hammer, where it rubs along inside the frame, but not so much that it'll run off under gravity and migrate elsewhere inside the frame. After you've lubed & reassembled the gun, you can rapidly & cycle the EMPTY gun's slide by hand several times, and then wipe off the oil that has run out at the rear of the frame rails. If the oil runs down and drips of the gun under gravity, you've used too much.
Too much can actually create functioning issues as it accumulates fouling and debris inside the gun. Just some thoughts.
Congrats again on the CS9. I have a friend who bought one of the early ones with the carbon steel slide, and he got it for $369 NIB, as I recall, which was a great price back then.
