The basic reason that we want to be able to measure power factor all comes down to one word – RECOIL! That is how much the gun “kicks” when you pull the trigger. While differences like gun design or weight of the gun can affect how much it kicks, a simple rule of thumb is that the higher number of power factor you have, the more your load will kick when fired. This is especially important in action pistol competition, where second and third follow-up shots take longer if you have more recoil to control. That’s why, to even the playing field, most competitors are always competing against others with similar types of guns, and similar power levels of ammunition.
So, I've got the bug. I won a stage recently and I'm deeper into this...perhaps later I'll dig even deeper.
I have a very rudimentary understanding of this concept, but I'm all about quicker follow up shots, less recoil, etc.
Assuming that we stick with factory loads...
Load A (1115fps x 124gr=138)
Load B (985fps x 147gr = 144)
Load C (1180fps x 115gr = 135)
So, based on PF, 115gr or Load C, right?
But then there's this...
Recoil is a function of momentum which tends to make heavier rounds recoil more heavily in a given caliber.
Momentum is actually a product of mass and speed, not mass alone. In other words, relative momentum is equivalent to the measurement of IPSC power factor. A 115gr bullet traveling 1130 fps has the same momentum as a 147gr bullet traveling about 880 fps. Both make minor power factor and can be used for production division. But which have the lightest "felt" recoil?
It takes MUCH less powder in order to move a heavier bullet the same power factor as a lighter bullet. Less power = less gas expansion = less energy. Remember that not all that energy is contributing to the momentum of that bullet. This is why I have never witnessed anyone (that is not a newbie) in production division who shoots anything lighter than a 147gr bullet. I shoot one heavier than that.
Contrast this to those who shoot 9mm open division with major PF. They want as much energy as possible in the form of huge volumes of gasses that will make their compensator work. So their trick is to use the lightest bullet allowed and stuff the most powder they can in a case while making major. While a great deal of that energy isn't transferred to the bullet, it doesn't end up going out the end of the barrel, but instead exhausts from the ports to compensate for the gun's tendency to flip up during recoil.
Ok, so recoil is based on pressures. Who measures chamber pressure?
Then there's this super wonky article.
Of course, there's the plastic striker fired weapon which weighs less and handles recoil differently than the full metal framed hammer fired pistol. It seems to be the consensus that strikers can be fired more quickly than hammers because of the DA initial stroke.
FWIW, I had shot 115gr prior to very recently. Bumped up to 124 and my penalty times decreased (moar practice, better glasses, or grains?). Unscientific, but I gotta shoot through some 124 for a while...
It's the off-season, but the holiday season means stocking up on ammo. What to do?