I'm new to this forum and unfortunately found it after searching about a problem I have with my P226R originally chambered in 9mm. I ran about 300 rounds of Speer lawman 9mm through the pistol. I love the gun and wanted one in 40sw for a backup to my rifle when hog hunting. I called Sig and they sold me a 40sw caliber exchange kit. Since my P226 is so new there is (was) no wear on the slide or frame rails. It looked brand new. I cleaned the rails, greased them up good like always, and installed the new upper that came direct from Sig with the 40sw caliber exchange kit. I ran 60 rounds of speer lawman 40sw through the firearm. The groups were terrible and I thought it was me. I usually run one ragged hole in the target with the 9mm upper. I removed the slide and there was a 3 inch gouge on the left side frame rail where actual metal was removed, shavings and all. It starts an inch back from the front and can be seen when the gun's slide is locked back. The rail is visibly thinner now. I am beyond bummed out. I called Sig and the rep said, "we don't promote the use of our caliber xchange kits." Seriously??? Why sell it then? Why make it at all?? And the guy that sold it surely didn't say that either and I was very specific that I wanted no issues or would go another route (buy a separate pistol). I've sent the pistol back to SIG and curious what to expect or if this is a normal QC problem. Seems I'm not the only one with this.