Fastbolt, how much are you paying through S&W for 3913 mag springs? Midway has them for $6 each and I always assumed that was close to factory direct pricing, but in the 10-packs, Wolff sells them for $4.80 a piece.

That's been the deciding factor for me since noticing it, but so far I have only tried their .45 mag springs (with success). Unless it's cheaper from the factory, I plan on ordering a 10-pack of 3913 Wolff's in the near future and trying them out with my CS9 and 4040 mags.