Scribe I just looked into this myself. The best answer I found was this.
Posted by Varminterror:
"No. The Ruger sr series pistols have a fitting collar machined at the end of the barrel for proper lock up, putting an over length sr40 barrel into an sr40c frame will leave the muzzle of the barrel loose fitting in the slide frame when closed into battery. It would likely function fine, but that slack would let the barrel float too freely, diminishing accuracy and increasing wear on the pistol, encouraging premature failure of the action."
http://rugerforum.net/gunsmithing/122901-sr40c-extended-barrel.html
It's just not an option for us.
