+P ammo and +P+
It’s more powerful so I should use it to shoot bad guys right?
Absolutely not! There is a lot of misinformation on this subject and I frequently get asked about shooting this ammunition, “occasionally, just for self defense, for training, hunting?”
Do not shoot +P ammunition in your gun, unless YOUR gun is stamped and or approved for +P and here is why. I have personally seen a revolver bend from +p ammo use when it wasn’t rated for +P. No it wasn’t a cheap revolver either. The gun stopped functioning correctly and after inspecting and taking measurements it was determined that the revolver had been damaged from shooting over pressurized ammo.
A long time ago in 1926 SAAMI the Sporting Arms and Ammunition Manufacturers Institute was formed to create (since there weren’t many) and “publish industry standards for safety interchangeability reliability and quality amongst the nation’s leading firearms and ammunition manufacturers. “
What that means to us is this. There is a standard for ammunition, dimensions and pressures amongst other things. This way if you buy ammo from Winchester for your gun it is dimensionally the same size as ammunition from Remington and it will fit that gun. It will also fit any other gun that is marked for the same caliber. That’s kind of a cool thing if you think about it. Yes, there were many chamber variants based on the same “caliber” prior to this. Go measure turn of the century firearms and you will see vast differences. Manufacturers were trying to make better performing ammunition for various reasons, as they still do today. There was a need for standardization and SAAMI accomplished it. One of the things they did was set a maximum average pressure for different calibers.
Chambers are tested at MAP or maximum average pressures. The pressures are measured in one of two ways. The newest acceptable test method is the piezoelectric transducer system. A transducer is mounted in the chamber of a test barrel. When the test cartridge goes off the case is crushed into the transducer and creates an electric charge that can be translated into a pressure reading. The second older way of measuring chamber pressures is CUP or copper units of pressure. A copper cylinder is crushed by a piston that is fitted in the chamber of a test barrel and when the round is fired the gas pressure pushes the piston and crushes the copper. The measurement is recorded as CUP. These measurements are then typically represented as PSI or pounds per square inch.
+P is an official designation for ammunition that is loaded to higher than maximum average pressures, and acceptable to shoot in firearms stamped +P. They have been TESTED! The more powerful ammunition will have higher velocities and therefore could penetrate different things better. (Auto glass, heavy clothing, tissue) Typical +P pressures exceed the MAP by 10%-20% but in some calibers upwards of 40% higher. So if your gun is not approved for +P ammo then it is most likely damaging the gun. Again, this pressure is higher than the MAXIMUM, not the normal pressure. This does not mean that the firearm will break the first time you shoot +P ammo; however you are most likely causing damage that you cannot see with the naked eye. Your firearm may break (this can mean explode into your face) the first and only time you shoot +P ammo but you will likely break it after several uses. What if it breaks when you need it badly? What if it breaks and explodes into pieces? It is not acceptable to use +P ammo in your gun unless it has been rated for +P ammo. If you are unsure of what ammo you can shoot in your gun then you need to consult your owner’s manual. (The owner’s manual is the paperwork inside the gun case that many people don’t ever read; coincidentally it also shows you how to take the gun apart for cleaning.) If you are still unable to locate this information I strongly suggest contacting the manufacturer and asking them. They all have 800 numbers and they are all on the internet.
So then there is +P+, yep you guessed it, even more powerful ammo. However, +P+ is NOT an official rating by any standard and therefore should not be used. How do you know how powerful this ammunition is since there is no official standard for the “rating” other than more powerful than +P ammo? If you want to break you $600 dollar Glock or $3000 custom built 1911 or your S&W snub nosed BUG that is not rated for higher than MAP, then by all means continue shooting +P or +P+ ammo out of it. I’m sure the gun store will be happy to sell you a replacement when your gun breaks. I also hope that your gun does not break from stress fractures in the chamber created from your “just sometimes” shooting of over pressurized ammunition when you need it to defend yourself. Honestly, shooting this over pressurized ammo sometimes, when you think you need to makes about as much sense as only carrying your gun into a bad neighborhood.
Remember that accuracy in a gun fight is more important than whether or not you shot the bad guy with +P+ ammo or just regular old 45 ACP 230 grain hollow points.