A discussion about energy - is it all equal?

[Eurodriver]

I was recently discussing SBR trajectories out to 500+ yards and noticed that out of a 10.3" barrel, M855 has almost twice as much energy at that distance than a 9mm does at the muzzle.

It got me thinking - aside from the obvious (bigger holes among different calibers) is a bullet with more energy going to do more damage than a bullet with less? If so, why does 5.56mm get such a bad rap?

Example:
Would M855 carrying 650 ft lbs of energy be more devastating to tissue than a 9mm carrying 380ft lbs? This may be a difficult question to answer (or easy) because the M855 is a steel core projectile while the 9mm most likely has expanding hollow point bullets. You get a .224" wound channel vs an almost 0.50" wound channel (with sharp edges, to boot) But how does the energy each round is carrying factor into this?


I understand that there is eventually a trade off, you can have a 30gr projecticle travelling at 4000 FPS, Or 3000kg boulders travelling at 5 FPS, which on paper would carry significant amounts of energy but the round may just disintegrate upon impact or the boulder would just push a guy out of the way. Let's ignore anomolies such as that for this discussion.

[vicious_cb]

I was recently discussing SBR trajectories out to 500+ yards and noticed that out of a 10.3" barrel, M855 has almost twice as much energy at that distance than a 9mm does at the muzzle.

It got me thinking - aside from the obvious (bigger holes among different calibers) is a bullet with more energy going to do more damage than a bullet with less? If so, why does 5.56mm get such a bad rap?

Example:
Would M855 carrying 650 ft lbs of energy be more devastating to tissue than a 9mm carrying 380ft lbs? This may be a difficult question to answer (or easy) because the M855 is a steel core projectile while the 9mm most likely has expanding hollow point bullets. You get a .224" wound channel vs an almost 0.50" wound channel (with sharp edges, to boot) But how does the energy each round is carrying factor into this?


I understand that there is eventually a trade off, you can have a 30gr projecticle travelling at 4000 FPS, Or 3000kg boulders travelling at 5 FPS, which on paper would carry significant amounts of energy but the round may just disintegrate upon impact or the boulder would just push a guy out of the way. Let's ignore anomolies such as that for this discussion.

Pretty much energy doesnt matter because energy in itself is not a wounding mechanism. All that matters it that the projectile has enough energy to perform a certain job. In the case of a 9mm hollow point, does the projectile have enough energy to expand then penetrate a given distance inside the target? With a 5.56 projectile the question to as is does the projectile have enough energy at the target to fragment? Will those fragments have enough energy to penetrate enough distance inside the target to cause an incapacitating wound? As long as the projectile has the minimum energy to perform a certain task like expand or fragment then penetrate to a lethal depth then doesnt how much more energy it has when it arrives at the target.

Since energy is proportional to velocity, having more energy means the projectile can do more work, ie expand, fragment, penetrate at a longer distance than a projectile with less energy at a given distance.

[markm]

why does 5.56mm get such a bad rap?

Because guns attract retards.

[Slab]

Because guns attract retards.

BEAUTIFUL

[vicious_cb]

"Impact energy is like a budget. If your budget is large, there is a lot that you can, but not necessarily will, do. If it is small your choices are limited." -http://www.dtic.mil/ndia/2008Intl/Spickert_Fulton.pdf

[Clint]

Terminal energy is easy to calculate, but only determines the potential to do work.

The projectile can waste that potential doing useless work like over penetrating , or it can use it to cause maximum tissue damage.

The difference is in how efficiently it couples to and destroys the medium it strikes.

Frontal area had a lot to do with this, as does velocity, bullet design and hardness.

[fedupflyer]

...F=MA...

[T2C]

I am a believer that energy transfer at a given distance is more important than potential energy from a projectile delivered from an individual weapon system. If the projectile stays inside the target and transfers all of it's potential energy, in most cases it is better than a projectile with much higher potential energy that passes through the target.

I am also a believer that 5.56mm gets a bad rap from people with poor marksmanship skills who expect a magic projectile to compensate for poor shooting techniques. In a few instances, personnel with good marksmanship skills are forced to carry a cartridge chosen by administrators, because it fills a wide variety of roles.

The 5.56mm has done the job for a lot of personnel who carried it when they went into harm's way over the past 40 years, so I would not criticize someone who prefers the round.

[markm]

I am also a believer that 5.56mm gets a bad rap from people with poor marksmanship skills who expect a magic projectile to compensate for poor shooting techniques.

I also remember reading some imbecile's comment on ARF years back. He'd seen sand box video of a soldier shooting into the front of a vehicle approaching a road block and wanted to know why the vehicle didn't just explode into flames.

[MegademiC]

Energy alone is meaningless. Many other variables give you a much better idea of effect, be it term ballistics, or external. A 55gr 223 fmj going 4k fps has a ton of energy, but will make a wound similar to a 22lr if it doesn't upset. There are also many examples of lower energy rounds producing better results than their higher-NRG counterparts, both real world and gel.