In the context of shooting sports, the term "power factor" refers to a measure of the energy or power of a bullet or cartridge used in competitive shooting disciplines such as IPSC (International Practical Shooting Confederation) and USPSA (United States Practical Shooting Association).
Power factor is calculated by multiplying the bullet's mass (weight) in grains by its velocity in feet per second and dividing the result by a constant value. The constant value varies depending on the specific shooting organization and division being competed in. Typically, the constant value is 1,000 for IPSC and USPSA, but it can be different for specific divisions or categories.
The formula for calculating power factor is as follows:
Power Factor = (Bullet Mass in Grains * Bullet Velocity in feet per second) / 1,000
Ex. - 9mm - 124 Grain Power Factor = 124 Grain x 1150 FPS = 142,600 / 1,000 = 142.6 you drop any numbers after the decimal place.
The purpose of using power factor in shooting competitions is to ensure that the ammunition used meets a minimum level of power or energy, thereby ensuring that the targets are engaged with sufficient force to be considered "powerful" enough to knock them down or activate scoring devices reliably.
Different divisions or categories within shooting sports may have different power factor requirements. For example, in IPSC/USPSA, major power factor is often required for higher-scoring divisions, while minor power factor is allowed for lower-scoring divisions. Major power factor typically requires a higher bullet velocity or heavier bullet compared to minor power factor.
Competitors need to calculate the power factor of their ammunition before a match to ensure compliance with the specific requirements of their chosen division. Failure to meet the required power factor can result in scoring penalties or disqualification from the competition.
It's important to note that power factor in shooting sports is distinct from the power factor discussed in electrical systems, as mentioned in the previous response.
IDPA Power Factor
The International Defensive Pistol Association (IDPA) has established specific minimum power factors for its divisions, which determine the required energy of the ammunition used.
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Stock Service Pistol (SSP) - Power Factor (PF) - 125: This division primarily includes mostly unmodified semi-automatic pistols in 9mm or larger calibers, with minimal changes allowed.
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Enhanced Service Pistol (ESP) - PF - 125: In this division, semi-automatic pistols in 9mm or larger calibers are permitted with specific modifications allowed in accordance with the rules.
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Custom Defensive Pistol (CDP) - PF - 165: The CDP division is dedicated to semi-automatic pistols chambered in .45 ACP, with certain allowed modifications.
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Compact Carry Pistol (CCP) - PF - 125: Semi-automatic pistols in 9mm or larger calibers with limited modifications are eligible for this division. The barrel length must not exceed 4.1 inches.
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Carry Optics (CO) - PF - 125: Semi-automatic pistols in 9mm or larger with a slide mounted optics
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Stock Revolver - PF - 105: This division comprises mostly unmodified revolvers chambered in .38 Special or larger calibers. The barrel length must be 4.25 inches or less.
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Enhanced Revolver - PF - 155: Revolvers chambered in .357 Magnum or larger calibers with specific allowed modifications fall under this division. The barrel length must not exceed 4.25 inches.
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Back-Up-Gun (BUG) - PF - 95: Semi-automatic single, double, or striker fire with use of 380 auto or larger calibers.
Please refer to the IDPA rule book for the latest power factor information and division rules.
USPSA Power Factor
In the United States Practical Shooting Association (USPSA), most divisions are categorized into Major and Minor Power Factors, which impact scoring based on hits outside the "A" zone. The following are the six USPSA divisions and their respective power factors:
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Open Division (O) - Major: 165, Minor: 125 This division consists of highly modified semi-automatic pistols with features like extended ported barrels and optic sights. Popular calibers include 38 Super Comp and 9mm Major.
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Limited Division (L) - Major: 165, Minor: 125 In this division, semi-automatic pistols undergo slight modifications and are equipped with standard length barrels and iron sights. The dominant load used is caliber .40 S&W.
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Limited 10 Division (L) - Major: 165, Minor: 125 Similar to the Limited Division, this division adheres to the same general rules, but imposes a maximum magazine capacity of 10 rounds.
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Production Division (P) - All loads are set to Minor: 125 The Production Division features essentially stock semi-automatic pistols with minor improvements allowed. The dominant caliber used is 9mm.
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Single Stack Division (SS) - Major: 165, Minor: 125 Semi-automatic pistols in this division have minimal improvements. Popular calibers used are .45 ACP and .40 S&W.
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Revolver Division (R) - Major: 165, Minor: 125 This division includes popular revolvers with specified improvements, chambered in .38 Special or larger calibers.
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Pistol Caliber Carbine (PCC) - Minor: 125 Permitted Calibers 9mm, 357 sig, 40 S&W, 10mm, or 45 ACP
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Limited Optics (LO) (Provisional) - Minor: 125 This division is for non-compensated, slide mounted optics, with a single action firing mechanism, 9mm or larger.
Please refer to the USPSA rule book for the latest power factor information and division rules.
IPSC Power Factor
In the International Practical Shooting Confederation (IPSC), divisions are categorized into Major or Minor Power Factors, which impact the scoring based on hits outside the "A" zone. The following are the 5 IPSC divisions and their respective power factors:
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Open - Major: 160, Minor: 125 9mm or larger caliber
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Standard - Major: 170, Minor: 125 9mm or larger caliber for minor, 10mm or larger for major
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Classic - Major: 170, Minor: 125 9mm or larger caliber for minor, 10mm or larger for major
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Production - Major: N/A, Minor: 125 9mm or larger caliber
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Revolver - Major: 170, Minor: 125 9mm or larger caliber
Please refer to the IPCS rule book for the latest power factor information and division rules.
Conclusion
While heavy bullets and fast powders produce a softer recoil push, there are shooters who prefer the snappier recoil of the lighter bullets. Some feel that the quicker recoil cycle gets them back on target faster. Those who understand the Power Factor can try both, and choose the load that works best for them.
Many people get confused when it comes to the power factor of the bullet you are using. Please look carefully on the above information or talk to one of your shooting buddies for advice and information.
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