There are differing opinions on this subject. Naturally, I think I have the correct one.
1. Factory +P is loaded well below maximum allowable chamber pressure. It is not a "hot" load. The typical +P is a 125 JHP at 925 FPS. Big whoop. A good target load in my opinion. The whole "+P" thing is marketing hype. I hear stories of a friend of a friend's gun shooting loose with +P but since this load is so mild, and so far below allowable pressure, I have a hard time understanding how this is possible.
2. Many folks use the model number as a guide, as in, if it has a model number stamped on it then +P is OK. But what is different about the first gun with a model number and the last without it? Nothing. No changes were made in the design or materials. They are the same gun save for the presence of the model number.
I use the year 1930. This is not a hard and fast date but is my best estimate. Prior to the middle 1920s the tempering of steel was an imprecise science. The Titanic may have sunk due to improperly tempered hull plates that tore open under pressure from the collision. I figure that if I use 1930 then I am safe.
Alloy or steel frame, J or K frame, I have no concerns whatsoever about factory +P (which is not a hot load anyway, remember) in a S&W made after 1930. Below is a 1942 Military & Police Model that was already well worn and much used when I got it. It is pictured with the 500 rounds of Remington +P and some of the 600 rounds of my own +P+ (125@1150 FPS) that I fired through it to see if anything would happen. It came as absolutely no surprise to me when nothing happened at all.
I think +P is all hype and unworthy of all the hand-wringing. Others will issue dire warnings about +P. You do what makes you happy.
