I have a Colt Agent, which is basically a Cobra with a shortened grip. My owner's manual from Colt says the Agent & Cobra are suitable for "limited use" with .38 Special +P ammo. The manual then provides this caveat...
"Extensive use of .38 Special +P ammunition will accelerate wear in your revolver. For continued satisfactory performance, have it checked by a Colt Authorized Repair Service Station periodically. Intervals should be every 1,000 rounds in aluminum frames and 2,000 to 3,000 rounds in steel frames.
NOTE: If you want to use +P+ ammunition, buy a Colt revolver chambered for .357 Magnum cartridges."
There has been a lot of speculation on this subject but as far as I know nobody has cited the manual as an information resource.
-Bob