Understanding Power Factor

Understanding Power Factor - How Relevent Is It?

by Josh Mazzola of Team AR15Targets

In USPSA, the term "Power Factor" (PF) is one of the many demons that new shooters have to conquer to adequately understand both the basics of the sport, as well as the more integral aspects of gaming and scoring - reference my post regarding speed vs accuracy in IDPA and USPSA.  So let's answer the basic question of "what is PF?"  In terms for the everyday person, the answer is deceptively simple; PF is the "energy" (in a non-mathematical sense) of your round, how hard or soft your specific ammunition shoots.  That's about the extent of the easy aspect of understanding PF, from here it gets a little more complex.

There are two levels of PF, Major (valued at 165PF and greater) and Minor (valued at 125-164.99PF).  While the different levels effect how shooters are scored in terms of target zone values, shooters are not separated into different divisions based on PF in USPSA.  In other words, a Limited-10 shooter with Minor PF competes directly against all other Limited-10 shooters in his or her classification (A, B , M, GM, etc) whether their ammunition makes Major or Minor PF.  PF itself is calculated by multiplying the weight (in grains) of the bullet, by the velocity with which is exits the muzzle, and then dividing that product by a constant of 1000.  So let's take the example of standard factory 9mm...

Winchester White Box:

(115grains X 1180fps) / 1000 = 135.70PF

At a match (usually only sanctioned regional size or larger) your ammunition will be chronographed and a bullet weighed, to establish your PF for the match.  Because of the fear of possibly not "making PF", most top shooters suggest never shooting an ammunition which is less than 5PF above your PF Floor (the lowest possible PF you can have and still be classified within a given PF).  So that would mean if a shooter was shooting Minor, he or she should shoot a minimum PF of 130 and if Major, a minimum PF of 170.  Also, most top shooters will not shoot an ammunition which comes in at much more than 5PF above their PF Floor.  Doing so incurs unnecessary increases in recoil which can add microseconds to times.  Cooking up loads that make PF and shoot extremely flat/soft is something many shooters spend countless hours testing in a very raw trial/error format.  Generally, 9mm is shot at Minor PF (unless in Open Division where some shooters load 9mm to Major PF - WARNING, be sure you gun can handle the increased pressures of a Major PF load before trying), and .40cal is shot at Major PF.

So should you shoot Major or Minor?

- It's first important to mention that if shooting Production Division, there is only Minor PF; regardless of how hot your load is, you will be scored Minor, so shoot a Minor load.  In Limited, Limited-10, and Open, shooting Minor means that you will need to focus more heavily on accuracy, to the point where it almost becomes trivial.  In order to keep up with the shooters who are at the top of the brackets in these divisions, you really need to be shooting major so that you can collect as many points as possible when you send a round into the C or D zone of a target.  It is widely considered a handicap to not shoot Major in these divisions - again, if you reference the above linked article, you will see that the cost of missing the A zone when shooting Minor is mathematically double that in terms of the direct translation of a point to time when compared to Major.  In Single Stack division, there is more debate over whether Minor is a handicap or not.  Minor shooters can actually utilize an advantage in magazine capacity which is negligible in L, L10, and O when shooting in SS.  Major shooters in SS can fit approximately 8 rounds in a magazine while Minor shooters can get up to 10.  That's a 20% advantage in magazine capacity (if we assume 10 to be the standard) that Minor shooters enjoy in SS; so the need to be more accurate can be balanced by magazine capacity.

What's the difference in 5PF - is such a small difference actually even noticeable? 

- Surprisingly enough, the felt difference in just a few PF deviation can be dramatic, specifically depending on  what powders are being used, how fast they burn, what bullet weight they are pushing, and what that then equates to in terms of slide reciprocation speed.  While everyone has their own recipe for loads, the standard for Production (where I've spent the majority of my time in USPSA) seems to always be a heavy bullet moving slower opposed to a light bullet moving faster.  In other words, shooters tend to opt for a 147grain bullet moving at 880FPS rather than a 95grain bullet moving at 1375FPS, despite the fact that both have a PF of approximately 130.  What this really breaks down to is that each shooter needs to find a load which works for him/her and the only way to do that is to test a bunch of different loads.

But what if i don't have the time to reload my own ammo?

- No problem!  Not only can you shoot factory 9mm in Minor and be competitive, you can also shoot factory .40cal in Major without any problem as they are both WAY above the PF Floor for both classifications.  If you are more competitive and are looking for every edge you can get, you can buy reloads from various websites which manufacture their ammo to meet certain PFs.  Atlanta Arms and Ammo is an awesome place to do this.  They offer some top notch ammo loaded to whatever you can think up in terms of PF.

So let's recap...as a new shooter, the most important thing that you need to consider relating to PF is what division you should shoot in.  If you are shooting 9mm, unless you are competent in understanding how 9mm Major will effect your gun and you are able to load 9mm to Major PF, you are most likely best off shooting in Production.  You will get a more adequate comparison of your skill-level to other shooters because you won't be at any disadvantage in terms of the value of hits.  If you have a .40 caliber, you should shoot in anything BUT Production.  You will be at a disadvantage shooting a .40 against 9mm's when your hit values are worth the same.  Even if you have to shoot factory loaded .40 in L or L10, you will be better off doing that than shooting factory loaded .40 in Production.