The original intent of .38 Special was a cartridge that would give somewhat improved performance over standard pressure loads. There was never a warning on -P ammunition as to what guns it should or could be fired.
THERE STILL IS NOT! It was, and is, safe to shoot .38 Special +P in any standard revolver chambered for .38 Special.
If there was an issue the ammunition manufacturers would place a warning on their boxes
The failure point with revolvers is the cylinder, not the frame.S&Ws "not tested for" is a CYA for their warranty, a lawyer answer, a way out so if there is a pressure related failure
not due to materials or workmanship, they can say "We told you not to do that" and avoid paying for losses related to pressure failures. In the past S&W has stated openly that their cylinders will not fail until a pressure level over 60,000 PSI, this is nearly four times the standard pressure level of 15,000 PSI originally and 17,500PSI now, and three times the +p level of 20,000.PSI.
(Added) BTW, .38 Special Proof Pressure is 28,000 PSI This is 140% of +P pressure. +P is only 9.5% higher than standard pressure.
(Added)There also was the .38-44 high pressure ammunition clear back to 1929. This developed approximately 25,000 PSI 25% higher pressure than +P. There was never a warning about using this ammunition in the then current either S&W and Colt models of revolvers, including the S&W Chief's Special introduced in 1950, that everyone is scared of shooting +P in now because of their age!
There was never an issue with +P ammunition until the internet and people started asking "Can I shoot +P in my .....? Then the unknowing began warning people like you about the dangers of +P and everything went in the toilet after that. Now almost everyone worries about +P.
Marked or not you can safely shoot +P in
any .38 Special. If you don't like the recoil then don't!

Shoot standard pressure loads all you want and carry +P in the gun when exercising your concealed carry rights.
I am not recommending that anyone shoot +P loads exclusively, just that they will not do any damage to the gun in moderation. Unfortunately moderation is something many American have no concept of, in anything!

It is an extremely valid notion, and will prevent trouble in many activities!
Like any mechanical device the gun will wear out sooner the more it is stressed, but we are talking 15,000 to 50,000 rounds, how many lifetimes will it take you to shoot this many? It is just like your car, it will last many years longer driving at 60 MPH than it would if you drove in 100 MPH.constantly, not even factoring in accidents.
I know, TMI unless you wanted to really know the truth!


