Depends on your gun. Check the manual.
Here's a whoops example:
[www.youtube.com/watch?v=yhkHML6LZv4]
+p there is no standard. it was designed for shorter barrels like 3.5 inch to ensure cycling and try and get the same velocity as a 5 inch.
+P+ is sub gun ammo.
+P all manufacturers make it to their spec.
most modern pistols can take +P. none use +P+ as a previous poster had to have a signoff for wheel gun only.
"I gots to have me 10% more pressure in my mouse gun!"
I've never understood that crowd. If standard pressure doesn't get the job done, 10% more isn't going to do it either.
Step up a caliber.
Yes there are a handful of guns that pretty much require +P. If your gun does not, you'd be smart to stay clear of it unless it's a full sized service firearm.
If you do this stupid stuff with a revolver, you'll end up stretching the frame to the point where the firing pin can't even contact the primer anymore... All this because someone is certain that 10% more pressure makes it a hand cannon.
Wrong.
There is no standard for +P+, there IS A STANDARD for +P.
+P is required for a couple specific handguns, like the kimber solo. It will not achieve the same velocity as standard pressure will with a 5" barrel, but it will generate much more wear and risk of damage to the firearm.
A wheel gun's frame WILL STRETCH the more you shoot it. +P ammo will insure this happens in 50-100 rounds instead of after 10,000 rounds. All for laughable velocity gains.
P++ is object oriented increased pressure.