Sigs chambered in .40 and .357 SIG are identical except for the barrel (P226 and P229)... magazines and all.
So if it's not reliable afterwards, it isn't the barrel.
If you're really concerned, get a factory SIG barrel for the conversion.
...but not all .40 slides can handle the power of .357 SIG cartridge (it's a much hotter round) and that's why there are problems with converting guns only meant to take .40.
Also, 357 Sig feeds much more reliably than just about any other pistol ammo due to its shape.
Last edited by thedudeabides; September 16, 2012 at 10:59 AM.