Overpressure ammunition

Because of this, +P ammunition is typically found in handgun calibers which might be used for paramilitary forces, armed security, and defensive purposes.

These loads were eventually dropped due to a combination of safety concerns, and newer smokeless powder rifle cartridges that offered even higher velocities, such as the .30-30 Winchester.

[2] The first modern smokeless powder cartridge deliberately loaded by a major manufacturer to higher than standard pressure was the .38 ACP, originally introduced in 1900.

Similar to the "rifle only" loads, the .38 Super could still be chambered in the older .38 ACP guns, therefore producing a dangerous combination.

Capable of reaching a muzzle energy of 500 ft⋅lbf (680 J), the .38 Super remains a viable defensive cartridge, though its usage is most commonly found in popular shooting sports such as IPSC.

[2][3] In the United States, standards related to arms and ammunition are maintained and published by the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI), which publishes standard internal pressures of calibers, formerly measured in copper units of pressure and currently in psi based on piezoelectric instrumentation.

The +P standard is designed so that if a shooter were to accidentally use a +P cartridge in a non +P rated firearm, the chance of a one-time explosive failure is minimal as long as the gun was in good physical condition.

There has been significant improvement in metallurgy and quality since the first guns in those calibers have been made, with the result that higher pressures are now safe in modern firearms.

These loads are generally designed to provide maximum performance from older cartridges, when used in newer, stronger firearms.

The 14,000 psi (97 MPa) limit for .45 Colt, for example, reflects the original black powder performance of the round, and is safe even in firearms built in 1873, when the cartridge was introduced.

However, these high-pressure loadings can only be used in modern firearms, because they are produced using higher quality materials and enhanced manufacturing techniques.

Because of the potential danger in shooting these "unofficial magnum" cartridges, they are generally only available if handloaded or purchased from low-volume specialty manufacturers.

In some cases, high pressure ammunition is restricted to law enforcement sales, such as Federal's .38 Special +P+ and 9mm Parabellum +P+ Hydra-Shok cartridges.

[citation needed] The use of +P or +P+ ammunition does accelerate wear and reduces the service life on the component parts on any pistol.