Overpressure ammunition
Overpressure ammunition, commonly designated as +P or +P+ (pronounced Plus-P or Plus-P-Plus), is small arms ammunition that has been loaded to produce a higher internal pressure when fired than is standard for ammunition of its caliber (see internal ballistics), but less than the pressures generated by a proof round. This is done typically to produce ammunition with higher muzzle velocity, muzzle energy, and stopping power, such as ammunition used for security, defensive, or hunting purposes.