Power factors?

[chad s]

Can someone briefly explain power factors to me. I see everyone in here talk about it. I have loaded for quite a while now, but never shoot competitions. Is there a formula for it or what. It might help me understand what is going on better in these forums. Thanks.

[D.Hayden]

A couple of discussions on this:

http://www.brianenos.com/forums/index.php?showtopic=17732

http://www.brianenos.com/forums/index.php?showtopic=15543

http://www.brianenos.com/forums/index.php?showtopic=8979

Basically (weight of the bullet x speed)/1000. USPSA minor = >125 - <165, Major = 165+

[chad s]

ahhh.. thanks, for now it is all clear to me. I will wonder no more. I tried a search, but it came up with like a million hits on power factor. I did read the links though, pretty helpful.

[stingerjg]

power factor is: Bullet weight x muzzle velocity=power factor

US power factors are as follows:

125,000 power factor floor for all divisions

165,000 or more for major power factor for L10, Limited and Open

an example of a production load would be:

9mm 124gr fmj at 1030fps would be 127,720 or 127.72PF, just above the power factor floor for production

an example of a major load would be:

38SC 125gr jhp at 1389fps would be 173,625 or 173.625PF

[.40AET]

power factor is: Bullet weight x muzzle velocity=power factor

Then divide by 1,000.

Bullet weight x muzzle velocity/1000=Power Factor

[Flexmoney]

I split off the fluff about "rounding numbers" so that we could focus on answering the basic question.

chad s,

Let me know if you need more info.

The bottom line is "power factor" is a measurement.

You need to know tow things to figure it out...your bullet weight (in grains) and your bullet velocity (in feet per second). You multiply these two things.

Whether you then divide by 1,000 or not isn't really important...that just moves the decimal point around.

Here is an example:

I shoot a 180g bullet.

I shoot my gun over a chrono and find that my rounds are going at 945 fps.

I just multiple those two numbers.

180 x 945 = 170,100

I am shooting 170.1 power factor.

[.40AET]

Flex- I was only pointing out that power factors are not discussed in terms of 100 thousands. You and I know to round it down, but maybe someone asking a question about PF doesn't know how to calculate it. I sure didn't want to generate another topic about rounding Vs. truncating. If your at 170pf you don't have to worry about going minor at a match from a math error.

[Flexmoney]

.40AET,

Your post was fine and dandy. No worries. I split out a bunch of other posts that were beyond the scope of this forum/question.

And, I only mention the option of dividing by 1,000 (or not) because not all the games do it the same way. Some choose not to divide.

[achard]

"Estimation Only"

If you want to change your load setting

let say your current pf is 180 and your current charge is 5.3

the computation

180 (current pf) / 5.3 (current power charge) =33.96 * 5.1 (new powder charge) = 173.19 (your new pf).

Chrono is still the best way.

rich

[Tman33_99]

Rich,

Your estimation works OK for small changes, but should still be verified w/Chono....but loads do not change linearly (i.e a 10% change in powder doesn't always equate to a 10% change in velocity). Always change in small steps and verify.

[achard]

Your estimation works OK for small changes, but should still be verified w/Chono.

Tman,

That's what I do after changing my loading charge I chrono to make it sure I make it to 170 pf. 173 to be safe