Power Factor, Recoil and the NEED for Speed

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Power Factor, Recoil and the NEED for Speed

Postby bignflnut » Wed Nov 14, 2018 10:39 am

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?
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Re: Power Factor, Recoil and the NEED for Speed

Postby JustaShooter » Wed Nov 14, 2018 3:44 pm

OK, so I ran some numbers using max powder charges for Unique and the various bullet weights and velocities you provided. Notice there is *not* that much difference in powder charge weight when dealing with fast-burning pistol powders - a total of 1 grain between the three powder charges. Keep in mind I'm not sure if the powder charges I used will deliver the exact velocities you gave, but relatively speaking we should be in the same ballpark. I used a 2lb firearm which is on the light side for a 1911-ish platform but on the heavy side for a polymer gun. Here is what I found using a recoil calculator at http://www.shooterscalculator.com/recoil-calculator.php

Load A using 5gr powder:
Recoil Impulse: 0.72 lbs-sec
Recoil Velocity: 11.66 fps
Recoil Energy: 4.23 ft lbf

Load B using 4.5gr powder:
Recoil Impulse: 0.74 lbs-sec
Recoil Velocity: 11.95 fps
Recoil Energy: 4.44 ft lbf

Load C using 5.5gr powder:
Recoil Impulse: 0.72 lbs-sec
Recoil Velocity: 11.66 fps
Recoil Energy: 4.22 ft lbf

Draw your own conclusions, but I doubt you could feel the difference between the 115 and 124 grain, and probably not the 147 either. Now, heat up those loads (which you might need to do to make major, I don't know but I have heard you need pretty high velocity 9mm loads to make major) and maybe that changes things, I don't know.
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Re: Power Factor, Recoil and the NEED for Speed

Postby Sevens » Wed Nov 14, 2018 4:17 pm

It is my opinion based on UNSCIENTIFIC hands-on many tens of thousands of rounds of experience that inly massive differences in felt recoil can be predicted or even shared with numbers and formulas but where it truly matters is getting your butt on a range and a timer in your ear.

The teeny little differences you show are meaningless in the real world, it's all about the actual recoil impulse and how it affects YOU with your particular handgun.

I've seen this hands-on so many times that I couldn't even possibly guess.

I say pick a load and shoot the wheels off it and establish a baseline. At some point, make a change and practice like hell and THEN see if you can pick up a perceptible difference.
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Re: Power Factor, Recoil and the NEED for Speed

Postby Sevens » Wed Nov 14, 2018 4:20 pm

Oops, forgot to mention...

As I said, the math and numbers mean very little to me, however it may be worth noting that if you are intrigued with the math... there is a guy who wrote a free iPhone app that measures recoil impulse for you if you own an Apple Watch.

I don't have one, no plans to get one. However the author of the app has written an exterior ballistics app that I do use and like a lot, he writes quality software.
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Re: Power Factor, Recoil and the NEED for Speed

Postby bignflnut » Wed Nov 14, 2018 4:31 pm

Sevens wrote:It is my opinion based on UNSCIENTIFIC hands-on many tens of thousands of rounds of experience that inly massive differences in felt recoil can be predicted or even shared with numbers and formulas but where it truly matters is getting your butt on a range and a timer in your ear.

The teeny little differences you show are meaningless in the real world, it's all about the actual recoil impulse and how it affects YOU with your particular handgun.


To that end, what do we think of the concept that one could track such movements?

Anybody got any Xperience with the X?


My concern is that I can do the range time thing and even have double blind magazines loaded at my direction, but without my understanding what is where, but my "results" would be relatively subjective, in that my "feeling" would be impacted (see what I did there?) by my groupings.
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Re: Power Factor, Recoil and the NEED for Speed

Postby steves 50de » Wed Nov 14, 2018 5:40 pm

Would this thread be a better fit in firearms and gear. :?: or training and tactic's :wink:
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Re: Power Factor, Recoil and the NEED for Speed

Postby Bruenor » Wed Nov 28, 2018 12:07 pm

It seems to be the consensus that strikers can be fired more quickly than hammers because of the DA initial stroke.

Ben Stoeger has won USPSA Nationals in production division for several years running and is using a DA gun with a hammer and not a striker fired gun, for whatever that's worth.
He started out with a Baretta 92 and was winning matches, and now shoots a Tangfolio Stock 2.

CZ's (SP01 Shadow and shadow 2) are very popular in production division as well. I think people tend to like the weight of the steel guns to help dampen the recoil as well.
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