I know that +P and +P+ ammo is hotter and faster than regular ammo, but what I don't know is what exactly determines if ammo qualifies to have one of these designators.  So far, I've thought of two possibilities:

1.  Powder amount in cartridge:  Perhaps "regular" ammo has up to X grains per round and +P has up to X + Y grains, and +P+ has up to X+Y+Z grains of powder.

2.  Different type of powder:  Perhaps the + stuff has a different, faster burning type of powder, but in similar amounts to regular powder.

As the arfcom saying goes, edumacate me.

Cases designed to handle the higher pressures and hotter powder charge weights.  There is +p load data out there using most common powders if you are a reloader.

+P amd +P+ are pressure ratings. +P ammo is loaded above regular SAAMI pressure specs. +P+ is even higher pressure.

For example, SAAMI max for 9MM is 35,000 PSI. +P is 38,500. +P+ is even higher, but does not have a SAAMI standardized max level. A generally accepted standard is that +P+ is loaded to no more than 15% higher pressure than +P, which would mean about 44,000 PSI in 9MM. Actual +P+ 9MM is usually loaded no higher than 42,000 PSI.

Since +P+ is loaded without an industry standard, it is usually only sold to LE agencies, and only after they have signed a release of liablilty for the ammo manufacturer.

These higher pressure level can be reached by either of the ways you mention, as well as some others (hotter primers, brass with less internal volume, tighter crimp).

I thought SAAMI also had an official +P rating for .45 ACP. Regular pressure is 21,000 PSI, +P is 23,000 PSI.

Don't shoot +P in a Glock, the barrels are only tested to work with regular spec ammo. If you want to go around shooting 9mm in +P or +P+, get a Beretta, their website says that the barrel and locking block are manufactured to withstand +p+ ammo.

+P and +P+ are for those with little pistol syndrome.....

Just kiddin' continue with the discussion.

MT

OK Maybe I'm mistaken. I must have read that from another site.

Quoted: OK Maybe I'm mistaken. I must have read that from another site.

Yes I agree.  At this point, M882 and +p+ are the rounds I use in my G17.