Is ft-lbs of energy relevant anymore?

[nrose8989]

I've been reading through the stickies and I have a question. I also did a search and came up with nothing.

Regarding handgun ammunition (specifically SD loads). Is the ft-lbs of energy of a given load relevant anymore? From the stickies, I see a trend that penetration is a more important factor (aside from shot placement), and see no mention of ft-lbs of energy.

[MK108]

...a pistol bullet needs to have some kinetic energy in order to penetrate well inside the living target...the largest part of the energy spent is useful to displace soft tissues away from its path...unfortunately such displacement is not a reliable mechanism of wounding...it depends on the characteristics of the tissues and the stress level on them...so the measurement of the KE spent is not a reliable method to rank which pistol bullet is better for self defence purposes...

All the best
Andrea

[WS6]

Within reason, as long as penetration is met, and relible expansion occurs, I think it is relevant. The agencies reporting higher effectiveness with the 357SIG vs. the 9mm even though they expand and penetrate similary corraborates this. Energy=Temporary Cavity. I view TC as an important mechanism in a psychological stop, which I think most "DRTs" really are, unless the CNS is involved.

[Glock17JHP]

The only thing I use ft. lbs. of energy for is to estimate RECOIL...

[DocGKR]

Over the past 25 years, I don't recall "ft/lbs of energy" as EVER being a relevant predictor of incapacitation or measurement of wounding effects...

Did I miss something?

[Nathan_Bell]

Over the past 25 years, I don't recall "ft/lbs of energy" as EVER being a relevant predictor of incapacitation or measurement of wounding effects...

Did I miss something?

The only things I have killed are animals, but cranking up the velocity does tend to make things "deader". Is this more of a function of larger temp/perm cavity and not muzzle energy?

[200RNL]

It seems that, at least in the case of the military over the past 100 years, the worldwide service calibers have ended up in the range between 200 and 350 ft lbs of muzzle energy, give or take one way or the other.

On the low end of the energy scale, expanding light weight bullets have inadequate penetration in the 200 ft lb category. Increase bullet weight and decrease expansion or using a non expanding wadcutter gets the 200ft lb cartridges into the acceptable range of effectiveness.

Going up over 400ft lbs of energy introduces weapon controlability, durability and muzzle blast problems that militaries find unacceptable in a general issue handgun.

[DocGKR]

You are out backpacking and suddenly a grizzly charges you--do you want to defend yourself with a .220 Swift 40 gr polymer tip bullet at 4200 fps or a .45-70 405 gr JSP at 1475 fps?

[Nathan_Bell]

You are out backpacking and suddenly a grizzly charges you--do you want to defend yourself with a .220 Swift 40 gr polymer tip bullet at 4200 fps or a .45-70 405 gr JSP at 1475 fps?

In that example, of course the Swift I wasn't specific enough, I was inquiring about increased velocity with the same caliber and in the examples I have the same bullet.

I was speaking from experience of going from a .375 H&H 260 Gr Accubond @~2400fps and a .375 RUM pushing the same bullet @ ~2900 fps. The first destroyed the heart and lodged in the spine of a black bear, the second made the thoracic organs into a Slurpy-like consistency.

Also have seen close to the same increase when going from factory .45/70 loads (1400fps) out of a revolver to a max safe load (~1700fps). Same bullets, 300gr Remington JHP. On whitetail the damage between these two loads is comparable to the bears mentioned above.

The velocity delta would lead me to believe that the massive increases in damage are caused by increased crush cavities, temp and permanent. The reason I asked about the ME is that the old timers swear that they see the innards churned up like that when the rounds stay put inside of the critters and do not make it all the way through.

[LOKNLOD]

Energy is a poor indicator of terminal ballistics in living targets, because the collision created when a bullet strikes flesh is inelastic (totally inelastic of the bullet stays in the target without passing through), which means that kinetic energy is not conserved, only momentum is conserved. With energy being dissipated by varying and rather unpredictable mechanisms, it's not a good metric for comparison.

On a side note, playing with the conservation of momentum equations can help explain why no matter how "bad-ass" one's chosen caliber is, it's just not in the physics for it to have any sort of literal "knock down" power against adult humans.