Power factor (shooting sports)

Power Factor (PF) in practical shooting competitions refers to a ranking system used to reward cartridges with more recoil. Power factor is a measure of the momentum of the bullet (scaled product of the bullet's mass and velocity), which to some degree reflect the recoil impulse from the firearm onto the shooter (see section on limitations).

Power factor is used in competitions sanctioned by the International Practical Shooting Confederation (IPSC), United States Practical Shooting Association (USPSA), Bianchi Cup, Steel Challenge and International Defensive Pistol Association (IDPA).

The power factor is based on the bullets momentum as it's moving through the air by measuring the bullet speed using a chronograph and measuring a similar bullet mass on a weighing scale, thereafter calculating the power factor by the formula:

The power factor can be represented using different units:

Since by definition 1 gram = 15.4323584 grains and 1 m/s = 3.2808399 ft/s, their product is 50.6310987 and the two units can be converted back and forth using the following relationship

and

Note that the table below are examples, and for the same caliber different bullet weights can be used. Bullet velocity depends amongst other on bullet weight, powder types used and barrel length for the particular firearm.

For all major shooting competitions, claimed power factors are checked by firing the competitor's gun and ammunition through a chronograph. The most common practice is for a competitor to provide a certain number of rounds to the Range/ Safety Officers at the beginning of the match day. During the course of the match, the Range/Safety Officers at the chronograph station will pull a bullet from the competitor's ammunition and weigh it. When the competitor arrives at the chronograph station, they provide their pistol and an empty magazine to the Range/Safety Officer who loads a number of rounds into the magazine and fires them through the chronograph to determine the ammunition's velocity. The power factor is verified against the competitor's claimed power factor. If a competitor claims major power factor and fails to achieve it, they are moved to minor and their targets are scored accordingly. If a competitor fails to make minor power factor, they generally can continue to shoot the match, but will do so for no score.

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