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Posted

Power factor is a number derived by multiplying your bullet weight times the velocity, then dropping the last 3 digits. E.G. a power factor (pf) of 135 might be a 9mm 124gr bullet traveling at a velocity of 1089 feet per second. Or it could be a 147gr bullet at a speed of 918fps. It might even be a .40s&w 165gr bullet going 818fps.

Does that help?

MLM

Posted
Power factor is a number derived by multiplying your bullet weight times the velocity, then dropping the last 3 digits. E.G. a power factor (pf) of 135 might be a 9mm 124gr bullet traveling at a velocity of 1089 feet per second. Or it could be a 147gr bullet at a speed of 918fps. It might even be a .40s&w 165gr bullet going 818fps.

Does that help?

MLM

That gives me the basic math, but what exactly does it mean? Is the number a measure of "stopping force or power" or is it a measure of accuracy, ect ??

Thanks for your reply.

Posted

To me all power factor is is an equation relating to the various shooting sports such as my favorite, USPSA. PF levels the playing field so to speak. I shoot production which has a minimum PF of 125 in order to keep shooters from loading super low recoil loads which would give them an edge. The open guns require much higher power factor for the same reason.

PF relates to stopping power, I guess. But that is not the reasoning behind it. You won't find , "165 Power Factor", on a box of factory ammo.

But the earlier answer explained it quite well. Bullet weight X velocity=PF. Only the first three digits count. Everything is rounded down, 124.9999999999999999 is still a PF of 124.

Posted
Power factor is a momentum value (with inconsistent units) that relates back to a recoil level.

Guy

Ahh, the red light comes on. Thanks for all the replies.

Gary

Posted
Power factor is a momentum value (with inconsistent units) that relates back to a recoil level.

Guy

Really not so much "inconsistent" as "non-standard".

Standard English units of momentum would be lb·s, which expanded to base units is slug·ft/s.

Grains are also a unit of mass (just like slugs), so grain·ft/s is equivalent, albeit with a goofy scaling factor.

1PF = 1000 grain·ft/s = ~0.00444 lb·s.

Posted
To me all power factor is is an equation relating to the various shooting sports such as my favorite, USPSA. PF levels the playing field so to speak. I shoot production which has a minimum PF of 125 in order to keep shooters from loading super low recoil loads which would give them an edge. The open guns require much higher power factor for the same reason.

Everything is rounded down, 124.9999999999999999 is still a PF of 124.

This really helps me as well. I had this discussion with a friend from work the other day. So correct me if I'm wrong, but the ideal situation would be to have the greatest power factor you can while not giving up too much control due to recoil?

Posted
To me all power factor is is an equation relating to the various shooting sports such as my favorite, USPSA. PF levels the playing field so to speak. I shoot production which has a minimum PF of 125 in order to keep shooters from loading super low recoil loads which would give them an edge. The open guns require much higher power factor for the same reason.

Everything is rounded down, 124.9999999999999999 is still a PF of 124.

This really helps me as well. I had this discussion with a friend from work the other day. So correct me if I'm wrong, but the ideal situation would be to have the greatest power factor you can while not giving up too much control due to recoil?

For competition, you want to get as close to the power factor as you can and still always be over the minimum. In terms of on-target perfromance, since PF is slanted towards momentum, it favors mass, so slow and heavy. Energy goes in terms of velocity squared, so PF is not really a good jusdge of on-target performance. PF for competition...Energy (and a bunch of other stuff) for on-target performance of a round.

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