Overpressure ammunition, commonly designated as "+P" or "+P+" is ammunition that has been loaded beyond the specification for that particular cartridge, but below the pressure used for a proof round. These loads are often used in pistol ammunition intended for self-defensive use.
Overpressure ammunition generates higher pressure than standard loadings. This propels the projectile at a higher velocity than normal, providing for generally improved terminal performance against some targets. The higher pressure also tends to cause more wear and tear on the weapon used to fire it; therefore, it should only be used in weapons that are rated to fire +P ammunition, and if this ammunition is used in a weapon that is rated to fire it, the maintenance schedule should allow for checking parts and replacing them as they wear out more often than would otherwise be required.