As far as the exact definition of +P and +P+ I' m not sure. I do know that there are only certain specific cartridges that can have the " +P" designator. I know for sure that .45ACP, 9mm Parabellum, and .38 Special all can have the " +P" designator. I also know for sure that, according to the SAMMI guidelines, .40S&W can NOT be loaded to " +P" as it' s already a high pressure cartridge, so if you see a box of .40S&W labeled " +P" they are just doing it for marketing purposes.

Basically, the " +P" designates that the cartridge is loaded right up to the maximun allowable SAMMI pressure. The " +P+" isn' t actually a SAAMI term, but actually denotes that the cartridge is loaded hotter than the SAMMI pressure spec. From the reading I' ve done it seems the cartridge most commonly loaded to " +P+" is the 9mm Parabellum, and that most NATO spec and a lot of LEO 9mm is +P+. Somebody likely realized that the SAMMI pressure specs for 9mm Para. was too conservative in modern guns, or they are nuts enough to push the SAMMI envelope.

During my research I' ve also discovered that +P really isn' t all that necessary for the .45ACP, as the gains from the marginal increase in velocity are offset by the sizable increase in recoil and muzzleblast, and the higher velocity could cause the bullet to expand too rapidly and reduce penetration. According to many opinions, the heavy fat .45 bullets just don' t need the speed that the smaller, lighter .357 caliber bullets of the 9mm and .38sp. I think I' m going to just go with the premium standard pressure JHPs. There is also several months to the Late ML/handgun season, and I might just decide to save a little cash and buy a .357Mag revolver. I' ve been wanting to get a centerfire revolver for awhile anyway.

Mike