9mm, 5.7, 40sw, 45acp and 44 magnum: energies, velocities and what do they mean?

[el Godfather]

Dear THR:
I wanted to ask you about the ft lbs energy, joules energy and velocity of the captioned calibers with respect to what do these numbers practically means.

How do you calculate the effect of say certain 9mm load's energy and velocity compared to any of the other calibers?

Also, what exactly foot-pounds measurement mean?

 

[moxie]

Yahoo and Google are your friends:
http://en.wikipedia.org/wiki/Foot-pound_(energy)

 

[rcmodel]

http://en.wikipedia.org/wiki/Muzzle_energy

http://www.handloads.com/calc/quick.asp

In actual practice, all the ammo companies have websites, and there they list the velocity & energy of every load they sell.

Also in actual practice, handgun performance is much better determined by bullet design, and penetration in ballistics gel.

You can have all the energy in the world, but if the bullet fails to expand and zips right through the target without transferring all that energy, it is pretty much wasted on the landscape behind the target.

rc

 

[el Godfather]

Moxie
On yahoo/google searches meanings can be found but no debate on what these number actually mean individually and together.

 

[moxie]

Then you want to investigate terminal ballistics. This is the "effect," as you say, of a bullet's mass and velocity, aerodynamics, it's frontal area and overall design, ballistic coefficient, and the target medium. The mass and its velocity create energy that has an effect or impact on the target.

A decent understanding of basic physics is needed. The formulas are available on line. The debate revolves around the relative importance of mass vs. velocity, of slow, heavy, bullets, vs. fast, lighter, bullets, and a myriad of other factors.

And, there have been numerous empirical studies and even tests on youtube. You might start with tnoutdoors and his ballistics gel tests:

http://www.youtube.com/user/tnoutdoors9?feature=results_main

One of the eminent researchers in the field of "wound balistics" is Dr. Martin Fackler. You might acquaint yourself with his work as well, beginning here:
http://www.rkba.org/research/fackler/wrong.html

After you've read all the studies and reviewed all the videos, and done your own chrono and media testing, come back and discuss your findings.

 

[jmr40]

In the real world how deeply the bullet penetrates, and the diameter of the hole, along with shot placement are all that matter. Energy numbers are 1 way to predict penetration and expansion, but they are not perfect. They don't take into consideration bullet construction, or diameter.

 

[Propforce]

In the real world how deeply the bullet penetrates, and the diameter of the hole, along with shot placement are all that matter. Energy numbers are 1 way to predict penetration and expansion, but they are not perfect. They don't take into consideration bullet construction, or diameter.

+1

Just a few points for thought

Energy out of muzzle is not the same as the energy delivered at point of impact

Energy delivered at point of impact is not the same as the energy absorbed by the BG

Energy absorbed by the BG is not the same as the energy to incapacitate the BG

Lots of variables as stated above.

 

[Skribs]

I'd also like to point out that velocity matters when you get over 2000 FPS. That is the threshold around where the stretch cavity starts to matter in addition to the crush cavity.

But in general, whether you're talking about a .357/.44 magnum or a lowly .32 ACP, it's expanded diameter and penetration that really matter. Higher energy values help, but bullet design is the more important aspect.

 

[M7]

Dear THR:
How do you calculate the effect of say certain 9mm load's energy and velocity compared to any of the other calibers?

There are mathematically-based models that can be used to make such calculations.

Two such models are-

http://www.amazon.com/Bullet-Penetration-Modeling-Incapacitation-Resulting/dp/0964357712

and

http://quantitativeammunitionselection.com

Hope this helps.