Power factor (shooting sports)

A high-speed photography of a .38 Special bullet fired out of a Smith & Wesson Model 686 revolver.

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 bullets mass and velocity).

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).

Calculation

The power factor is based on the bullets momentum, given by the formula:

$\mathbf{p} = m \mathbf{v},$

Where (imperial units are used in competitive shooting sports):

• p is the momentum in "kilo grains feet per second" (kgr·ft/s)
• m is the mass in grains (7,000 to the pound)
• v is the velocity in feet per second (ft/s)

Power factor is one thousandth of the momentum found above. Thus we arrive at the formula:

$Power\, Factor=\frac{mass\,[grains] \cdot velocity\,[ft/s]}{1000}$

The power factor can also be calculated exactly using the metric units gram for bullet weight and meter per second (m/s) for bullet velocity, which divided by 1,000 gives the derived SI-unit Newton second (kg·m/s) for momentum. Since by definition 1 g = 15.4323584 grains and 1 m/s = 3.2808399 ft/s, their product is 50.6310987 and the following formula can be used:

$Newton \, second = \frac{mass \, [g] \cdot velocity \, [m/s]}{1000}$

$Power \, Factor = Newton \, second \cdot 50.6310987$

Examples of different loads

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.

Cartridge	Bullet mass (grains)	Muzzle velocity (ft/s)	Power Factor	Bullet mass (gram)	Muzzle velocity (m/s)	Newton seconds
9x19 mm	116 gr	1,150 ft/s	133.4	7.5 g	350 m/s	2.625 Ns
.40 S&W	155 gr	1,200 ft/s	186.0	10 g	366 m/s	3.660 Ns
10mm	220 gr	1,250 ft/s	275	14.3 g	381 m/s	5.448 Ns
5.56 NATO	62 gr	3,100 ft/s	192.2	4 g	945 m/s	3.780 Ns
7.62 NATO	175 gr	2,590 ft/s	453.25	11 g	790 m/s	8.690 Ns
12 gauge	1.125 oz (492.1875 gr)	1,200 ft/s	590.625	32 g	366 m/s	11.712 Ns

Verifying During Competition

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.

At local (often referred to as "club") matches, it is rare to verify the competitors' claimed power factor, except to ensure the minimum caliber is met (e.g., a USPSA Limited shooter using a 9mm bullet and claiming Major power factor).

Various shooting organisations

International Practical Shooting Confederation

IPSC and USPSA provide for two power factors, Major and Minor. The basis for use of power factor in scoring is the assumption that, in a real-life encounter, a center of mass hit with a bullet of any power will suffice to end the fight. Lesser-power cartridges will have less effect as the hits land further from the center. Targets are divided into scoring areas (labeled A, C, and D) that roughly align with vital areas of human anatomy. Hits are scored thus for areas A, C and D respectively: Major; 5-4-2. Minor; 5-3-1. In this way poor hits (i.e. less-accurate marksmanship) are penalized with a greater penalty applied to less powerful cartridges/loads.

In USPSA as of 2014, a value of 165 or greater is considered Major, while values below 165 are Minor.^[1] Until a point in the late 1990s, the cut off point for "making Major" was 175.

All firearms must have a power factor of 125 or greater for IPSC/ USPSA competitions; almost anything of 9x19 mm or greater caliber will meet the minimum required power factor. This minimum power rule is designed to mitigate the speed and accuracy advantages of smaller calibers. Less-powerful cartridges have lower recoil and thus can be fired more quickly with accuracy; setting a minimum value requires all contestants to use some recoil management skills.

The desire to "make Major" is a large part of the popularity of high velocity 9 mm cartridges in this type of competition. .38 Super and other similar cartridges can be loaded to make Major power factor. The felt recoil of a 9 mm at Major is much the same as it would be for a .45. However, its higher operating pressure (.45: 17,000 PSI, .38 Super: 34,000 PSI) provides the Super a greater amount of higher-pressure gases to the muzzle brake. Open Division pistols are allowed to have a muzzle brake, and the redirected gases act to dampen felt recoil and muzzle rise. Other handgun divisions are not permitted muzzle brakes, thus the .38 Super or one of its derivatives (e.g., 9mm Major or 9x23) are not common outside of those two divisions. In all divisions except Open and Revolver, the minimum bullet diameter to "make Major" is 10 mm/ .400" (i.e. .40 Smith & Wesson can be used), except that Australia currently has a provisional exception to allow .357 Sig to make Major because it is the largest caliber most can use.

In IPSC Handgun competitions, Open, Standard, and Revolver can have either Minor or Major scoring, while the Production division only recognizes Minor scoring, and following that the use of Major ammo will not give any scoring advantage. Major/ Minor scoring also occurs in the USPSA in Open, Limited, Limited 10, Single Stack and Revolver divisions. In the USPSA Production and Carry Optics divisions, only Minor scoring is recognized.

Division	Power factor	Ns
IPSC Handgun minor	125[2]	2.469 Ns
IPSC Handgun major (Open)	160[2]	3.160 Ns
IPSC Handgun major (Standard, Classic, Revolver)	170[2]	3.358 Ns
USPSA Handgun major (Open, Limited, Limited 10, Single Stack and Revolver)	165	3.259 Ns
IPSC Rifle minor	150[3]	2.963 Ns
IPSC Rifle major	320[3]	6.320 Ns
IPSC Shotgun	480[4]	9.480 Ns

Steel Challenge

A minimum power factor of 120 was required to activate the stop plate in years past, which stops the time. The minimum power factor rule no longer applies.

International Defensive Pistol Association

The IDPA also has different power factors, and they are calculated the same way, however there is no scoring distinction as in USPSA. A particular IDPA division has a minimum power factor, and the firearm must meet or exceed this minimum to be legal for competition. The minimum power factor is 125 for all divisions, except Custom Defensive Pistol (which is restricted to semiautomatics chambered for .45 ACP), which has a power factor of 165.^[5]

In all instances, it is up to the competitor to ensure his/her ammunition meets the requirements for the competition or equipment Division.

Effective 1/17/11 the power factor for the stock service revolver division (SSR) was reduced to 105 since most factory produced .38 special ammunition available on the market did not meet the previous minimum power factor of 125.^[6]

NRA Action Pistol

In the Bianchi Cup, all matches requiring the use of centerfire ammunition must meet or exceed power floor of 120,000, or 120 Power Factor.

See also

• Muzzle energy

References

1. "USPSA Rule Book, Appendix D1" (PDF). USPSA. Retrieved 24 June 2014.
2. IPSC.org - The Handgun Divisions List
3. IPSC.org - The Rifle Divisions List
4. IPSC.org - The Shotgun Divisions List
5. "IDPA Rule Book, Appendix One" (PDF). IDPA. Retrieved 7 April 2014.
6. "IDPA web notice". IDPA. Retrieved 31 January 2012.