+P+ is generally considered to mean the pressure exceeds that of accepted industry specs for +P, but that's all it means. There's no official "upper" industry limit, so there's no way to know by how much the pressure exceeds the commonly used industry standards. Buyer/user beware.
Back in the early days of my S&W armorer training we were told to use whatever issued ammunition was provided by our agency ... with the presumption being that any +P and +P+ 9mm ammo used was going to be produced by one of the major American ammo makers who provided contract ammo to LE/Gov agencies, and who had a vested interest in not blowing up the common major maker pistols used in LE.
Back then it was also common for LE buying higher pressure ammo to sign a waiver accepting responsibility for using the higher pressure ammo, meaning any increased wear & tear, etc.
It's also a really good idea to consider any warnings or prohibitions offered by a gun maker when it comes to the ammo the gun company considers appropriate or inappropriate for use in their gun.
We were also told that the use of such +P+ 9mm ammo could not only accelerate normal wear & tear, but to watch for deformation caused by the higher recoil forces propagating throughout the pistol.
One example which we were specifically told to be alert to seeing was the possible deformation of the 3rd gen pistol slide stop lever assemblies. We were told that the increased recoil forces might result in the eventual outward or inward change of the angle of the slide stop lever in relation to the assembly's frame pin. In other words, the original 90-degree angle of lever-to-pin might increase or decrease, potentially causing different functioning problems at some point.
Back in those days we were taught how to use a vise and lead babbitt bar to "adjust" (judiciously whack) the angle and restore it, if necessary. Later on the instructors just told armorers to replace a tweaked slide stop assembly with a new one. The inference seemed to be that the factory may have decided that some armorers might lack the skill and experience to properly "adjust" an assembly, which is understandable when you remember that only being a factory trained armorer is NOT the same thing as being trained as a gunsmith. It was also a lot faster to replace an assembly than to spend bench time trying to "adjust" one, and the assemblies were inexpensive (sometimes free) and plentiful back in those days. Why waste bench time that might be useful for some other need, right?
Since the factory can't know what +P+ ammo is going to be used, it's easier (liability-wise) to just say that it's not approved for use.
Now, in my last Glock recert class, we were told that when the factory test-fires each new Glock, they use 2 standard pressure rounds and 1 proof round, and the definition of "proof round" meant 130% of standard pressure.
After the Shield 9 had been released for a while, I was told by a couple of different factory folks that while the use of +P was acceptable for use in the Shield 9 (albeit that it would accelerate wear and tear), the use of +P+ ammo was NOT approved.
In my last Glock class a Glock employee said that the G43 could be used with +P+ ... but then later on I heard from someone else in the field that they'd recently been told by Glock that the use of +P+ in the G43 wasn't recommended, and the reason seemed to be that it could cause increased slide velocities that might lend itself to feeding/functioning issues.
Now, I was issued 147gr standard pressure, 124gr +P and 127gr +P+ duty ammo at various times throughout my career when I carried S&W pistols. I used that ammo in all of my S&W and Glock pistols, and still do. I also replace recoil (and other) springs at shorter intervals and inspect for any signs of increased wear and tear of parts and assemblies.
One of our members here used to work for ISP, who used the pioneer major maker 115gr +P+ loads for many years as a duty load in S&W aluminum-framed pistols.
Now, personally, I've come to avoid using anything labeled +P+ that isn't made by one of the major American ammo companies who have invested a lot of years of R&D and have acquired a lot of successful experience in the production of +P+ duty ammo for LE/Gov agency users.
I tend to consider the +P+ designation for 9mm (and .38SPL) ammo as meaning something akin to "Here Be Dragons" in the margins of old world maps. You know it's
higher pressure than +P, but you don't know by
how much ...
Nice hearing from you.
