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Widder, SASS #59054

Power Factor vs. Muzzle Energy

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There are methods to determine Power Factors and there are methods to determine Muzzle Energy.

 

I am familiar with both methods BUT, when determining basic Power/Energy of your particular

firearms potential, is one method better used over the other?

 

EXAMPLE:

IF a .357 magnum load using a 125 grain bullet at XXX velocity renders a 200 PF,

would that basically be equal to a 10mm, 165 grain bullet at XXX velocity rendering the same 200 PF?

 

Thanks for any insight some of you might have.

 

..........Widder

 

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Just add a confuser.  Believe Nonte added bullet  diameter to the equation.  Velocity X Bullet Weight X Bullet Diameter       GW

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I look at muzzle energy as well as downrange energy. I can’t wrap my head around power factor.

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caliber is not usually a factor in power Factor.

 

125 grain bullet gives 200PF at 1600/sec.

165 grain bullet gives 200PF at 1212'/sec.

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Posted (edited)

Power factor is effectively momentum and thus proportional to recoil.   Energy is related to the damage a bullet will do to it’s target. 

 

Since energy is 1/2mv2 you can increase energy by increasing speed or bullet weight.   By increasing velocity you increase energy more than recoil while increasing bullet weight increases both equally. 

Edited by Still hand Bill
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Posted (edited)

     Its been a long time since Ive messed with this.

    Power factor is a great way for shooting sports to compare recoil for loads in like-type firearms. That's why you have different power factor categories. It appears unfair for someone shooting a stage with say 9mm to complete with someone shooting it with 45acp. So if you have a vaquero in 45colt and a vaquero in 357 and want to know which one has more recoil you can do the formula m•v and divide by 1000. Keep in mind this is different from "felt recoil".

     The way I do energy is mass times velocity squared and then divide that by 450,437. So on the non scientific calculator you can punch velocity times velocity equals. Times mass in grains equals. Divide by 450,437. 

 

    More to the point of what I think you want to know is: You can determine how a bullet might wound a live target by using the Hornady index of terminal standard. It is:

Square of the bullet weight times the velocity divided by the square of the bullet diameter divided by 700,000

 

Atleast I think that is what you were wanting. A way to tell the theoretical difference in various loads and their effectiveness on a live target. Keep in mind it would have to be like-type rounds. It wouldnt work comparing a round nose solid to a hollow point, but it would work comparing a 9mm hollow point vs the same type hollow point in 10mm or 45 or etc.

 

 

 

 

Screenshot_20190513-130156_Chrome.jpg

Edited by Tennessee williams
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Thanks EVERYONE.

TN:  I'm gonna work your formula and see how some of my .357 SIG loads compare with some of my

10mm loads.

 

..........Widder

 

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2 hours ago, Widder, SASS #59054 said:

Thanks EVERYONE.

TN:  I'm gonna work your formula and see how some of my .357 SIG loads compare with some of my

10mm loads.

 

..........Widder

 

Let us know how they compare.

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Posted (edited)

Energy can be deceiving the .22 Hornet and Remington 405 gr. Factory loads have the same Energy according to the charts ,,,,,,,,,,,,,,,,,,,,,,,,,but which one do you want in your hands when the bear with lunch on his mind is coming your way ....

Neither ,,,,,,,,,,,,,,,,,,,,,,,,, I push the 400 gr . Speer "Hot core" out the Muzzle of my Marlin 1895 at 2,100 FPS ....

This load produces a little over 3,900 Foot Pounds of Energy.....

 

Jabez Cowboy

Edited by Jabez Cowboy,SASS # 50129

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29 minutes ago, Jabez Cowboy,SASS # 50129 said:

Energy can be deceiving the .22 Hornet and Remington 405 gr. Factory loads have the same Energy according to the charts ,,,,,,,,,,,,,,,,,,,,,,,,,but which one do you want in your hands when the bear with lunch on his mind is coming your way ....

Neither ,,,,,,,,,,,,,,,,,,,,,,,,, I push the 400 gr . Speer "Hot core" out the Muzzle of my Marlin 1895 at 2,100 FPS ....

This load produces a little over 3,900 Foot Pounds of Energy.....

 

Jabez Cowboy

The same energy comparison is not material in the ability to kill a bear. It's what happens to the projectile after it hits (which has to do with energy retention/ability to penetrate to a vital). Both release the same energy into the bear, but one may be at 1" and the other 8". A massive hematoma under the skin will not kill a bear.

 

If your talking about steel knock down targets, the .22 and 405 should have close to the same capacity to knock the target over. But this still depends on the type of bullet and it's ability to transfer the energy to the target vs. lead splatter.

 

Ever recover your bullets after hitting steel? Bullets that retain more mass, transfers more available energy to the target. You will notice this when a shooters bullet rocks the whole target stand vs just the plate. A .45/.38 with the same energy has the same knockdown potential, but a slower .45 will hold together and transfer more energy to the target than a .38 traveling much faster that vaporizes and sends more energy to the ground around the target.

 

You can even hear it, if you listen.

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1 hour ago, Jabez Cowboy,SASS # 50129 said:

Energy can be deceiving the .22 Hornet and Remington 405 gr. Factory loads have the same Energy according to the charts ,,,,,,,,,,,,,,,,,,,,,,,,,but which one do you want in your hands when the bear with lunch on his mind is coming your way ....

Neither ,,,,,,,,,,,,,,,,,,,,,,,,, I push the 400 gr . Speer "Hot core" out the Muzzle of my Marlin 1895 at 2,100 FPS ....

This load produces a little over 3,900 Foot Pounds of Energy.....

 

Jabez Cowboy

Cant really use energy to calculate a kill factor. Not the HITS formula I put above. That formula is a better comparison. See how the .22 hornet compares to the 405 gr load using that one.

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As far as when Ol' Ephraim is concerned, I'd rather have the .45-70-405 at any velocity than that .22 Hornet...given the choice.  But the Hornet will do the job...if you stick it I his ear, or eye.  Bullet placement is as important as all the energy computations.  Of course, that doesn't apply to paper or steel plate targets.  In point of fact, the only reason we care about power factor is as it affects competition in events. 

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