What he said.No, don't believe that would work. The 9mm slide is not big enough to handle the pressure generated by the 357 or 40 caliber round.
If you had a 229, 9mm, you need the the wider, heavier slide to use 357 SIG or .40 S&W.
As Subhuman mentioned NO .22 conversions were made for the P225A1, and the only switchable slides between models, would be the P220, and P227, in .45 Auto. Subtle differences in Take Down notches, and Slide Catch notches, plus Disconnector cutouts prevent slide swapping. Locking Insert design and a barrel's lower lug design, must be compatible to work, in tilting the barrel into lockup in the ejection port.What 22LR conversion kits would work on a P225-A1? I would assume a P229 would work. Any others? I'm new to the P225-A1, and pretty new to handguns.
... unless you purchase a .357 Sig or .40 S&W X-Change Kit (which consists of slide + barrel + recoil guide rod and spring + sights, and a single magazine). At least, this is the case for the M11-A1 and newer P229's.The 226, 239 and 229 ... As stated before, if you buy the 9mm version of any of them, you are stuck with 9mm, you can't convert up.
You can buy a CPO pistol for what an exchange kit cost... unless you purchase a .357 Sig or .40 S&W X-Change Kit (which consists of slide + barrel + recoil guide rod and spring + sights, and a single magazine). At least, this is the case for the M11-A1 and newer P229's.