are all power factors the same?

[beastmode_05]

so im shooting 9mm and im wondering what are everyone's opinions on felt recoil 

if power factor is the same is there a perceived recoil difference between 115, 124, 147g 

[Joe4d]

you also need to factor in powder type.. a 124 gr bullet loaded to 130 pf with power pistol will be alot harsher than the same load loaded with say AA#2
With a generally fast powder though, half a dozen of one 6 of the other.. Sights will react a bit difference, things will feel different,, but come on,, were are still talking mousefart loads in 40-50 oz guns.. People get feel preferences, but probably mostly mental and doesnt amount to much on the score board

 

[Guy Neill]

Power factor is a momentum value. The units are not consistent, but momentum is a weight in motion. Historically momentum is defined as mass times velocity. Power factor is a weight times a velocity.

 

Thus, if the power factor is 130, the momentum is the same regardless of the bullet weight. Obviously, the velocity will differ to keep the power factor the same for the different bullet weights.

 

A 130-power factor translates to a momentum of 0.681.

 

The difference between the bullets is the time the bullet is in the bore. For the 115gr the bore time is 0.000605 sec. The 124gr bullet is close, at 0.000652 sec while the slow 147gr bullets take 0.000773 seconds to travel the bore. I used a 4.5" barrel for this comparison.

 

Historically this is where we describe the light, fast bullets as having a snappier recoil versus the slower, heavier bullets with each giving the same power factor.

 

[perttime]

The lighter bullet at higher velocity gives a faster recoil impulse. The heavier bullet at lower velocity gives more of a soft push, in comparison. Some prefer the former, others prefer the latter ... and some just don't worry about it.

[shred]

The simple answer without going into lots of physics is "yes", but there's not one "Best".  Try some different weights and see what you and your pistols like.

 

[Racinready300ex]

It's all feel and what you like. I think light weight guns might benefit from the perceived softness of heavy bullets. Where as a lot of these new LO 2011's that are pretty heavy might be better with the faster feeling lighter bullets.

 

But it's all pretty subjective and what you like. In reality once you get used to your load it's not going to have any real effect on the outcome of your match assuming it works in your gun 100% of the time. 

[Dr. Phil]

    A long time ago I discovered that different powders yield different muzzle rise arcs. I called it 'recoil arc' because back then ('83ish) there was no information aside from waiting 1 or 2 months for the magazine to come. I found that certain powders gave a quick snap of rise and others gave a slower more rhythmic arc. Recoil (to me anyway) is not crucial because that's what pushes back into the hand. The muzzle rise (or jump, flip, whatever) is what slows down the 2nd shot.

    Nowadays with all of the metrics on shooting it's easy to forget the 2 things that really matter; are you sights on the target when you press the trigger and did your trigger press disturb the sights? The muzzle should come back on target (or on the next target) on it's own. 

    FWIW my testing (and many others) says that the same PF with a heavier bullet yields less muzzle flip or a longer, slower recoil arc. In the case of my revolver in SC I have found that a 96gr bullet and a light load of Win 231 yields very little recoil. I think that's due to a 50ish oz gun more than the explosion within. That's not science, probably, but that's what 40 years has shown me.

I can usually tell when somebody is shooting 115s in their 9mm. The report is sharper. When you watch the muzzle flip you can usually see the quick rise. Kind of like a compensated gun compared to non-compensated. My load is actually the same in my 929, autos and PCC for 125 and 135 bullets. Makes PF.

    Works for my guns, loads, purposes. YMMV.

[superdude]

Tests show that the recoil force is different with different bullet weights when using the same gunpowder.  Heavier bullets produce slightly less recoil. 

 

https://www.shootingtimes.com/editorial/power-factor-recoil-bullet-weight-gives-edge/99399

 

 

[Joe4d]

10 minutes ago, superdude said:

Tests show that the recoil force is different with different bullet weights when using the same gunpowder.  Heavier bullets produce slightly less recoil. 

 

https://www.shootingtimes.com/editorial/power-factor-recoil-bullet-weight-gives-edge/99399

 

 

junk test.. they used a hollow base on the 185 vs regular base on the others to make the results turn out more significant by requiring more powder than a flat base would need to reach velocity.

[Guy Neill]

The powder charge factors into the recoil and comprises a significant part of recoil. 

 

As you would expect, the more powder charge, the more recoil.

[MoNsTeR]

The most general answer is "find out what you prefer and shoot that".

 

My answer is closer to Guy's above: heavier bullets mean less powder, less blast, less perception of recoil. I think if you try 135s or 147s you'll like them.

[Guy Neill]

As an example of the powder charge affecting recoil, using a 1.48n lb gun with a 9mm 124gr bullet and a muzzle velocity of 1050 fps, the free recoil energy is 4.86 ft-lb. This is with 4.3gr of powder.

 

Removing the powder, and keeping everything else the same, the free recoil energy lowers to 3.64 ft-lb.

 

Of course, with no powder there is no recoil.

 

However, in this example, the powder comprised a bit more than 25% of the total recoil.

 

In rifles it's a larger percentage with the larger charge weights.

 

[zzt]

Having had this conversation before:  same primer, same powder, different charge weights to get to say 132 PF:  147s produce the least actual recoil,  135s next, then 124s the 115s, etc.  Plug it into the formula and see for yourself.

 

For 'felt' recoil, 115s hit your hand hardest, then 124s, 135s and 147s.  So if you are looking for the absolute lowest actual recoil, and the least felt recoil, shoot 147s.  Then take a nap while the sights return.

[-JCN-]

15 hours ago, Guy Neill said:

Power factor is a momentum value. The units are not consistent, but momentum is a weight in motion. Historically momentum is defined as mass times velocity. Power factor is a weight times a velocity.

 

Thus, if the power factor is 130, the momentum is the same regardless of the bullet weight. Obviously, the velocity will differ to keep the power factor the same for the different bullet weights.

 

A 130-power factor translates to a momentum of 0.681.

 

The difference between the bullets is the time the bullet is in the bore. For the 115gr the bore time is 0.000605 sec. The 124gr bullet is close, at 0.000652 sec while the slow 147gr bullets take 0.000773 seconds to travel the bore. I used a 4.5" barrel for this comparison.

 

Historically this is where we describe the light, fast bullets as having a snappier recoil versus the slower, heavier bullets with each giving the same power factor.

 

You seem like you know your way around a physics book. 
 

I only remember general concepts. 
 

Can you help me?

 

I was trying to reconcile power factor versus kinetic energy where velocity is more of a factor. 
 

And springs and angular momentum. 
 

I guess what I’m asking is:

 

Is power factor a gaming convention or is it more meaningful than kinetic energy of a load?

[davsco]

i always thought, perhaps incorrectly, that energy (1/2mv^2) was a more applicable measurement for felt recoil / muzzle jump than power factor/momentum (m*v).  seems borne out by saying heavy but slower bullets have less recoil than lighter but faster bullets, when both are loaded to the same pf.

[Guy Neill]

In the defensive world, stopping power is based on momentum. Energy seems to place too much emphasis on the velocity. That's not to say velocity cannot play a role, as it is a part of momentum. Rifles likely have better success with velocity, given things like the Weatherby magnums.

 

However, stopping power is based on momentum. Momentum is also the means to determine the gun velocity when we are working toward free recoil energy.

 

Power factor is, as mentioned, a momentum number, but with in-consistent units. It is a shorthand means of looking at the power of the gun and was first developed to be an easy determination of the power, corresponding to what was seen in real life defensive gunfights.

 

So, on one hand it is a gamer function, but it has roots in real world.

 

The real trick may be setting the limits for the power factor. It has been toned down some over the years. Currently 165 for Major, 175 years ago.

 

[Farmer]

7 minutes ago, Guy Neill said:

In the defensive world, stopping power is based on momentum. Energy seems to place too much emphasis on the velocity. That's not to say velocity cannot play a role, as it is a part of momentum. Rifles likely have better success with velocity, given things like the Weatherby magnums.

 

However, stopping power is based on momentum. Momentum is also the means to determine the gun velocity when we are working toward free recoil energy.

 

Power factor is, as mentioned, a momentum number, but with in-consistent units. It is a shorthand means of looking at the power of the gun and was first developed to be an easy determination of the power, corresponding to what was seen in real life defensive gunfights.

 

So, on one hand it is a gamer function, but it has roots in real world.

 

The real trick may be setting the limits for the power factor. It has been toned down some over the years. Currently 165 for Major, 175 years ago.

 

Do you think the reason for the decrease was for safety reasons? I knew a fellow that shot IPSC years ago and remember him saying that there were quite a few kaboom’s because guys were pushing things a bit too hard. 

[shred]

Eh, most of that was unsupported chambers in .38 Supers with well-used brass.  Once ramped chambers came in it wasn't much of a thing.  The drop to 165 (160 / 170 for IPSC) seemed like it was more to get 9x19 to make Major although there were a raft of "reasons" given at the time.

 

 

[Guy Neill]

Yeah - things were pushing limits back then. 38 Supers using 115gr bullets and loaded to Major were operating at proof level pressures. Gun technology had not yet learned how to reliably set up guns to run with Major 38 Super loads and "Super Face" was all too frequent.

 

The Germans, as I recall, wanted the Major power factor to be 185. They also wanted to pretty much 100% test ammunition - which didn't leave much to shoot for the match.

 

With the gunsmiths learning to put the guns together, combined with supported chamber barrels I feel developed things to the point of offering safe shooting. This led to new cartridges, namely the 356 TSW and 9x23 Winchester that were made to utilize the high pressures. Rule changes at the time killed them from competition.

 

New powders are available that can deliver the velocities at more reasonable pressures.

[Joe4d]

3 hours ago, zzt said:

Having had this conversation before:  same primer, same powder, different charge weights to get to say 132 PF:  147s produce the least actual recoil,  135s next, then 124s the 115s, etc.  Plug it into the formula and see for yourself.

 

For 'felt' recoil, 115s hit your hand hardest, then 124s, 135s and 147s.  So if you are looking for the absolute lowest actual recoil, and the least felt recoil, shoot 147s.  Then take a nap while the sights return.

LOL,,   yeh centered on the Keyhole the first shot left.  
OP
Dont go overboard buying 147's.. at really low power factor some guns wont stabilize them especially the cheaper bulk plated bullets you may end up wanting to use.

[sharko]

5 hours ago, zzt said:

For 'felt' recoil, 115s hit your hand hardest, then 124s, 135s and 147s.  So if you are looking for the absolute lowest actual recoil, and the least felt recoil, shoot 147s.  Then take a nap while the sights return.

 

I would agree with this but minor 9 doesn't have much recoil anyway. I like the faster (snappier) 115's. I think I think of recoil on a 9 more in terms of muzzle rise and never notice hit on my hand. A lot of people say 147's recoil less but I've tried them several times and it always seems like more recoil to me.

As far is muzzle rise heavier rises more, may be slower rise but is still more too. I learned this years ago loading 45 Colt in a SAA, I started with 255gr bullets and it shot 6" high at 25yds, then I tried 230gr and got 3" high but 200gr were right on.

Came to the conclusion it was time in the bore. Don't notice that much difference on modern guns with zero change but then they usually grip much better than those Sigle Actions. 

 

[sharko]

2 hours ago, Joe4d said:

LOL,,   yeh centered on the Keyhole the first shot left.  
OP
Dont go overboard buying 147's.. at really low power factor some guns wont stabilize them especially the cheaper bulk plated bullets you may end up wanting to use.

 

Well that was my observation also, could never get as good of accuracy with 147's and only good accuracy with 124/125's if I pushed them fast like 357Sig or major.

[zzt]

5 hours ago, sharko said:

 

Well that was my observation also, could never get as good of accuracy with 147's and only good accuracy with 124/125's if I pushed them fast like 357Sig or major.

 

So, use JHPs.  You can buy them in bulk for less money than good plated.  Super accurate.  I agree on the 147s. Get them up to 144 PF and one hole groups at 25 yards.

 

FWIW, my bullseye shooting friends tell me you have to drive 9mm fast to get bullseye accuracy.

 

FWIW2, RMR 124 JHPs over Sport Pistol or AA2 for 132 PF are superbly accurate.  I bought 1k just to try them.  I'm back to 115 JHPs now.

Edited March 26 by zzt

[Dr. Phil]

The 147s can be problematic. The length can inhibit function in tight chambers and short chambers. They can raise pressures and (as mentioned) can be hard to make accurate sometimes. 

That is the reason I went to 135s. They are a good blend of function and accuracy and recoil/flip. If i am out of 135 I load 125, same charge and COAL,

I also shoot .357 or .358 in the guns which allow it. Revolver mostly but I have a couple autos that like that diameter. My PCC wants only .355 but I just switch to them at loading. I use the same charge/crimp whether .358 or .355.

[shred]

My take for Minor is 147s are soft but flippy, 115's are a bit too snappy, 124's are where it's at-- but it's different for everyone.  

 

Last Nationals equipment surveys show a big peak in 147/150 gr, then a slightly smaller one at 124/125 and the other weights much less popular.