Just to update this thread ...
I recently decided to take my CS45 (with one of my M&P 340's) to my range session to renew my LEOSA form. I'd planned on also shooting my original 4513TSW (6-rd mags), but got busy and didn't take it.
I did, however, end up having half a dozen of the loaded 6rd 4513TSW mags, which I'd already stuffed into my range bag.
So ... I decided to go ahead and use them to finish off the afternoon session using my CS45.
I've previously posted that I experienced some feeding stoppages using the 6rd 4513 .45 mags (without the second indentation) in my CS45 some years ago (when the stainless model had just been released). I didn't have the same experience while doing so for this last, current range session.
As best I can recall, those problems occurring many years ago were also in the time period when I was still shooting +P loads in my small .45's, and I remember trying some different +P's for a while in my CS45 and 4513TSW back then.
For this recent range session I was only shooting some 230gr RA45T (standard pressure SXT/T-Series) and 230gr Remington Golden Sabre. No +P's. While I only fired less than 50-60 rounds through the 4513's 6rd mags in my CS45, I didn't have any feeding issues using those mags.
I'm not curious enough to dig out some +P's to try in the CS45 again, although I still have some 200gr Speer +P and RA45TP (+P) in my ammo stock. I'll continue to carry the dedicated 6rd mags made for the CS45, and the other 6rd mags made for the 4513TSW in that gun (as well as using some 7rd mags made for the newer 4513 & 457 as spares for the older 4513).
I suspect the increased recoil force and slide velocity caused by the +P's, in the CS45, might be pushing things a bit when it comes to feeding "timing" in the 6rd mags made
without the secondary indentations (and S&W engineers did seem to think they were important enough to add to the CS45 mags
).
Like a couple other guys, I ordered a couple of the CS45 mags from Midway and saw that the side not visible in the factory packaging exhibited some weirdly done indentations, not evenly applied compared to the opposite side of the mag body. Having had some early issues with unevenly stamped indentations many years ago, in a few of the early mags that were reportedly hand-stamped, I didn't even feel like bothering to test them out. They immediately got returned. (Easy folks to deal with at Midway, in my case.)
I think I counted either 12 or 13 CS45 mags scattered among my various drawers, boxes and cabinets, so I'm probably good for as long as I own the CS45.
I bought a lot of them in earlier years when I was trying to wear out the CS45.
I did, however, pick up 2 or 3 new 3913 & CS9 mags from them.
I don't quite have a dozen each of those mags, and I own both a 3913, a CS9 & a new production 3913TSW, so having more mags is probably handy.