Quote Originally Posted by joepistol View Post
..." you might be able to convert your 9mm to a .40/.357SIG with an exchange kit. I'm not 100% certain on this, though."

I learned that a Glock 22 /40 S&W ( can I say this in a Sig thread ? ) can be converted to shoot 9mm with a conversion barrel (i.e. Lonewolf)
but a 9mm Glock can't be converted to 40 S&W, as the bolt face is too small, for the wider .40 case.
I'd think the same would be true for Sigs..unless the Sig conversion includes a new slide.

but I have been wrong before.. ( at least once)
You're both correct. The OP of your quote mentioned an "exchange kit", which is an entire upper in Sig's nomenclature. The used to sell "exchange kits". A different upper is needed to use .40 S&W or .357 Sig in a Sig factory P229 9mm. That's due to the P229 9mm slide having a smaller opening for the barrel. Same as you mentioned for your Glock.