From the Ruger Web site FAQs:
What type of ammunition should I use in my Ruger 9mm pistol?
The Ruger 9mm pistols are chambered for the 9x19mm NATO Parabellum (9mm Luger) cartridge, compatible with the U.S. and foreign military or commercial 9x19mm loads manufactured in accordance with NATO, U.S., SAAMI, or CIP standards, including high-velocity, subsonic, tracer, hollow point, ammunition loaded in aluminum, steel, or brass cartridge cases, +P and +P+ ammunition. Note: The LC9™ is not rated for +P+ ammunition.
I have referenced the above a few times in discussions of +P and +P+ 9mm ammo here. After reading Eagleks post about never seeing a reference to +P+ ammo in a manual
I would have bet the egg money that my SR9c manual said exactly the above. I would have then been without eggs. What it says is this:
The SR9c (TM) pistols are compatible with all factory ammunition of the correct caliber loaded to U.S. Industry Standards, including high-velocity and hollow-point loads, in brass, aluminum, or steel cartridge cases. No 9mm Parabellum ammunition manufactured in accordance with NATO, SAAMI, or CIP standards is known to be beyond the design limits or known not to function in these pistols.
The difference in language on the Web site compared to my manual is interesting. Since there seems to be no defined standard for +P+ 9mm (or any other caliber) the Web answer does not make sense to me.
Since a quality +P load is as much gitty-up as need, I won't let it worry me. Just an FYI.