[Tactworld45]

A friend of mine was asking me last night about reloading and the difference in energy with heavier bullets. He had a hard time understanding how a lighter bullet could produce more energy than a heavier one. Needless to say it turned into a math lesson on the coffee table. Once I showed him the calculations he had a better understanding of how kinetic energy comes into play.

I thought this would be useful information to those that might not be as familiar with reloading and ballistic data as others. You can use the equation below and plug in you own data to find the energy of the particular ammo you choose.

Foot pound of energy is calculated from Muzzle velocity squared multiplied by the bullet weight in grains divided by 450240. (4502420 is the only constant in this equation)

Example: 9mm Federal 124gr. Hydro Shock ammo

124 gr. w/ 1120 muzzle velocity

1120 x 1120 x 124 = 155,545,600 / 450240 = 345.47 foot pounds of energy.

Example: 9mm Federal 135gr. Hydro Shock ammo

135 gr. w/ 1060 muzzle velocity

1060 x 1060 x 135 = 151,686,000 / 450240 = 336.90 foot pounds of energy.


An interesting side note is that a heavier bullet will carry more energy at longer distances. In most cases at distances beyond 50 yards (impractical for most handguns) lighter weight projectiles will not produce the same kinetic energy of a heavier one.

At 25 yards, according to Federal’s velocity data the 135gr. round overtakes the lighter 124gr. bullet. As the caliber increases the yardage typically increases too.

 

[__jb]

Good post!

That formula is the whole premise behind the military going with a small 5.56mm M16 round... But with lots of gun powder...

 

[sfguard]

It didn't take me half that math to figure out I didn't want to get shot by any of them LOL. Seriously good post though

 

[NWGlocker]

Nice info. It's interesting to see how many caliber war threads are out there and not as many of these arguments take into account bullet velocity and total energy in the projectile. Big caliber bullet in a snubbie will have less kinetic energy than that .223 coming out of a rifle barrel at high speed.

 

[Rowdie]

Good info, Tactworld. Thanks fo the post.

 

[Tactworld45]

Good post!

That formula is the whole premise behind the military going with a small 5.56mm M16 round... But with lots of gun powder...

You are exactly right. I was doing some figuring tonight playing around with the numbers. Getting shot with a 63 grain 5.56 nato round is roughly equivalent to getting hit with a 30 pound cinder block at just over 37mph. That's going to leave a mark. LOL

 

[NWGlocker]

You are exactly right. I was doing some figuring tonight playing around with the numbers. Getting shot with a 63 grain 5.56 nato round is roughly equivalent to getting hit with a 30 pound cinder block at just over 37mph. That's going to leave a mark. LOL

I don't know which projectile would be worse. Messy either way :O

 

[Otintx]

Getting shot with a 63 grain 5.56 nato round is roughly equivalent to getting hit with a 30 pound cinder block at just over 37mph.

That's going to leave a mark. LOL

OUCH !

Thnkx for the math lesson, very good info, Sir !

Ot

 

[OklahomaSafeShooting]

All the above is correct but please also remember two other important numbers.

Sectional Density

Ballistic Coefficient

Both play importance in energy and flight

 

[__jb]

All the above is correct but please also remember two other important numbers.

Sectional Density

Ballistic Coefficient

Both play importance in energy and flight

Correct... Lots of factors determine the overall effectiveness of each individual round... Some of them are open to interpretation, otherwise we'd all be shooting the same exact ammunition... Here are a couple of Wiki pages for "extra credit" reading if anyone is interested...

Sectional density - Wikipedia, the free encyclopedia

Ballistic coefficient - Wikipedia, the free encyclopedia

 

[rangerbluedog]

If you think about it, it really is quite an interesting engineering problem. I know some folks have addressed this with penetration depth in balistic gelatin. A number I hear tossed about is 13-18" depth is a good number.
The Kinetic Energy only tells part of the story. If a fast moving bullet overpenetrates, and goes completely through the target, then all of that extra KE is not used up in the target. A common engineering equation is the enegy balance equation: basically states that the sum of energy imposed equals the sum of energy exhausted. So if the bullet doesn't stop in the bad guy, the extra KE is wasted and does you no good. The bullet must penetrate far enough to reach vital organs, but not so far as to exit the target. Kinda makes me think of the sport "curling" for some reason...
Sorry if this has been discussed before. I don't see it mentioned much anywhere. This post probably makes no sense - I'm sleepy...
Thanks for this interesting thread Tact.
http://www.rathcoombe.net/sci-tech/ballistics/wounding.html
Good article discussing this topic. Makes a good point about engineering efficiency vs. real world effectiveness.

 

[Tactworld45]

You do make a good Point Rangerbluedog. I agree with you. This is why I don't understand why the UN and Geniva Convention mandate only ball ammo in battle. Its supposed to be considered more humane. I see it to be a greater potential for wounding rather than a quick kill. I wonder how many soldiers foreign or domestic have been shot and survived because of non expannding rounds. I know I would rather live than die, but a non expanding round induces a greater possibility for unnecessary suffering. After all arent soldiers trained to kill not wound? What is the point of having such a powerful round if all the energy is wasted?