What is power factor?

[Blazer]

Can someone please explain to me what "power factor" is exactly, why is it used for major/minor, for that matter what is major/minor - where is each used?

How does one determine power factor, the average velocity of say, ten shots times bullet weight? lowest velocity? etc. Thanks. Bob

Sorry if this is such a newb question.

[Chills1994]

bullet weight in grains multiplied by velocity in feet per second.

Typically it gives you a number in the 100 or 200 thousands.

I just drop the 3 digits to the right of the comma and call it a 133 or a 172.

The thing with USPSA is to "grade" ya on Accuracy, Power, and Speed (time) , which are the three latin letters you see:

D.V.C.

If you're shooting a more powerful round called "major" then you get rewarded with more points for a non "center mass" hit.

If you're shooting "minor" you get "dinged" by earning fewer points with shots that would just "wing" a target.

And since you're shooting a less powerful round which yields less recoil and muzzle flip, you should be able to shoot faster.

Someone here on the forum has a signature line like:

DVC is a three legged stool. Remove one leg and you're just left with a pile of sticks.

That's a good analogy.

That all translates into "hit factor", which is points divided by time.

[HoMiE]

Quick little video that touches on PF and major/minor/hit factor.

Power factor is dependent on the game/division you play. For USPSA, Production division, everyone is scored minor with minimum PF of 125. In IDPA, SSP and ESP have a minimum PF of 125 as well (but they say 125,000, USPSA just divides by 1000 to get same number). For major in USPSA, you have to have a minimum of 165 and IDPA CDP division is 165 as well.

The procedures for calculating PF are kind of long, but quick version goes like this. IDPA - Shoot 3 shots over chrono, 2 of 3 must make minimum PF for division. USPSA - 8 rounds are collected, 1 bullet is pulled for weight, 3 rounds are shot over chrono, for 3 round average. IF PF is not meet, 3 more rounds are shot taking highest 3 round average. If PF is still not met, last round (1+3+3=7, you have 1 bullet left) is shooters choice. You can have bullet pulled and weighed hoping it is heavier or shoot it hoping it is faster if you have still not made the minimum division PF.

Edited December 24, 2008 by HoMiE

[Blazer]

Thanks guys, I think I've got it now. Very informative video.

[DarthMuffin]

One other comment on this, that personally I found rather fascinating (since I'm a geek and have some physics classes under my belt), is that power factor is a measure of the bullet's momentum (mass * velocity). A bullet's effectiveness is generally measured by it's kinetic energy, which is mass * velocity^2 (the ^2 means squared).

If you look at the two forumulas, better energy is obtained by a lighter bullet traveling faster (square the velocity -- it essentially counts twice). Better momentum is obtained by a heavier bullet traveling slower (compared to as needed for energy). This is why a 165PF load with a 155 grain bullet recoils more than a 165PF load with a 180 grain bullet -- energy is higher even though momentum is the same.

There are obviously practical limits for both -- too light of a bullet and it will be unstable and/or break up before it can penetrate it's target. Too heavy and slow and you'll have to shoot artillery style

As for why shooting sports use momentum for a metric rather than energy, it took me a while to figure this out but the reason is two-fold. The first is due to the steel, you need to transfer a certain amount of momentum to the steel to knock it over. The big reason is that back when the sports were started, chronographs were pretty exotic equipment so power was measured by an apparatus involving shooting some steel and seeing how far it moved -- which is a measure of momentum.

What does this all mean? Nothing really, I just find it interesting

Edited December 24, 2008 by DarthMuffin

[Steven Cline]

Quick little video that touches on PF and major/minor/hit factor.

Power factor is dependent on the game/division you play. For USPSA, Production division, everyone is scored minor with minimum PF of 125. In IDPA, SSP and ESP have a minimum PF of 125 as well (but they say 125,000, USPSA just divides by 1000 to get same number). For major in USPSA, you have to have a minimum of 165 and IDPA CDP division is 165 as well.

The procedures for calculating PF are kind of long, but quick version goes like this. IDPA - Shoot 3 shots over chrono, 2 of 3 must make minimum PF for division. USPSA - 8 rounds are collected, 1 bullet is pulled for weight, 3 rounds are shot over chrono, for 3 round average. IF PF is not meet, 3 more rounds are shot taking highest 3 round average. If PF is still not met, last round (1+3+3=7, you have 1 bullet left) is shooters choice. You can have bullet pulled and weighed hoping it is heavier or shoot it hoping it is faster if you have still not made the minimum division PF.

Hey! That's me. I'd never post myself (I know the greatness that walks these hallowed halls), but to be linked by someone else is really cool!

PhoneCop

aka DeadeyeSteve

[Blazer]

Very good job! helped me a lot. Keep up the good work. Thanks.

[Duane Thomas]

Another satisfied customer!

[Blazer]

Just found that DeadeyeSteve has quite a few very informative videos on youtube.