Re: CHANGE RECOIL SPRINGS FOR SIG P229?
I cannot speak to the SIG P229.
The Glock 27, 33 (.40, .357) use the same recoil spring assembly. The same is true of the G 23 and G 32.
One word of caution. Get a .357 SIG magazine or put a .357 SIG follower in your .40 S&W mag to shoot the SIG cartridge; or do not fire the last round out of the magazine.
It has been my experience with Glocks (using a .40 S&W mag) that the last .357 SIG round off of the .40 follower can "stump its toe" an be driven much deeper into the cartridge case on the loading stroke. If this happens, and the round is fired, you can experience significant over-pressure problems!