Fpe questions

[MaxMan]

If a bullet hit a 180 lb target generating 360 fpe. Does the target go over,? I don't think so as looking at police shooting baddies the baddie takes a couple of hits and doesn't go down. What are the physics of this.?

 

[kmoore]

Spell out what you mean by FPE. I understand FPS, (feet per second) and Energy as in (foot pounds).

 

[MaxMan]

I meant Foot pounds of energy. Sorry.

 

[blume357]

Nope, it took me a while to understand the physics but if the bullet leaving the gun does not have the energy to knock down the person shooting it then actually it does not have the power to actually knock down what it is hitting. The actual 'knock down', if it occurs, will be the body responding to the bullet hitting certain organs and reacting to that.

 

[Mobuck]

Probably not a 'knock down' by actual physical energy transfer.
Here's an interesting tidbit: When testing Federal TSJ or TPJ or whatever they call the polymer coated handgun ammo, I discovered that the 150 grain 9mm would literally PUSH the water filled jugs I was using as test media several inches across the gravel driveway. Each 2.5 gallon jug equals 20# (+/-) and these slow flat nose bullets would move 3-4 of them. This is a case of momentum being a factor of terminal performance and is impressive but not directly relatable to soft tissue damage.
If this bullet struck an object that was dense enough to stop the bullet, this energy transfer would be noticeable. This is different than a bullet that transfers it's energy by expanding laterally.

 

[Dan in MI]

Nope, it took me a while to understand the physics but if the bullet leaving the gun does not have the energy to knock down the person shooting it then actually it does not have the power to actually knock down what it is hitting. The actual 'knock down', if it occurs, will be the body responding to the bullet hitting certain organs and reacting to that.

I have used that explanation for years to get the point across.

Beyond that break a supporting bone, or it falls the" shootees" response.

 

[MaxMan]

Nope, it took me a while to understand the physics but if the bullet leaving the gun does not have the energy to knock down the person shooting it then actually it does not have the power to actually knock down what it is hitting. The actual 'knock down', if it occurs, will be the body responding to the bullet hitting certain organs and reacting to that.

Opposite but equal reaction? Sounds like the energy is dissipated gradually .

 

[kmoore]

No direct answer to the question. But humans when shot by handguns don't fly back like in movies. They drop if the shot takes out the central nervous system.
I will answer in a different way.
Handguns: FBI has spent millions over years studying "stopping Power." Think of a handgun bullet creating a wound or hole in the human body. If that bullet can create a wound channel 12 inches to 18 inches deep, FBI says that about as good as it gets to stop a human. They have left out "Stopping Power or FPE".
Their reports are online you can and should read through some or all.
Shorten FBI Quote: "Stopping power is irrelevant because no one has been able to define how much power, force, kinetic energy is needed to quickly stop a determined attacker." 2014?
With handguns look for testing that is pushing a bullet into gel at least 12 inches from 10 feet of muzzle and no more than 18 inches. Forget the min or max FPE needed to get that bullet there. At one point FBI said 14 inches was min.
Forgot to point out, a .45-caliber hole/wound channel 12 inches deep is normally much better than a .22 caliber hole that might get to12. More FPE is better than less, A bigger wound channel is better than a smaller one. If it's within the 12 to 18 inches.

 

[MaxMan]

Thank you. The movie reference is valid. I guess the term "man stopper" is actually reserved for ac12 gauge with something like buck and ball.

 

[Mobuck]

If you want to visualize the effect, just watch hunting videos (or pay attention while hunting). How often do you see a deer 'knocked of it's feet'? What is the typical reaction? A flinch and several seconds of full out flight before expiring. A deer is approximately same size as a human plus a greater likelihood of a double lung hit and/or broken shoulder with bone shards adding tissue damage.
One should expect no more (and likely far less) terminal performance/effect from a handgun which produces half or less foot pounds of energy on target.

 

[kmoore]

If you want to visualize the effect, just watch hunting videos (or pay attention while hunting). How often do you see a deer 'knocked of it's feet'? What is the typical reaction? A flinch and several seconds of full out flight before expiring. A deer is approximately same size as a human plus a greater likelihood of a double lung hit and/or broken shoulder with bone shards adding tissue damage.
One should expect no more (and likely far less) terminal performance/effect from a handgun which produces half or less foot pounds of energy on target.

Yes, that's a great way to explain it.

 

[BearBiologist]

FOOT pounds of energy is a misnomer. A 357 bullet (~ 1/3 of an inch) is 1/36th of a foot, therefore striking impact energy would be ~10 lbs. Not enough! Muscle and nerve response may cause the target to crumple, or maybe not.

Energy is good, bullet construction better, placement is supreme. All three is near perfect!

 

[BearBiologist]

I had a drill sergeant once tell me a human being is easy to kill compared to a deer!

 

[Mobuck]

^^^W/o going into brutal details, your DS was generally correct. BUT (darned near everything has a BUT) the OP reference was whether 360 foot pounds of bullet energy would knock over the target weighing half that in actual pounds. No reference to final outcome. Since there was no comment as to full or partial penetration, I assumed partial allowing 100% of the energy to be dissipated within the target.
A 100# deer can often absorb over 1000 FPE and hardly flinch.

 

[owldo]

"Stopping power is irrelevant because no one has been able to define how much power, force, kinetic energy is needed to quickly stop a determined attacker."

I would argue that a 12ga 00 high velocity buck shot ... within shot gun range would be my definition ! IMHO !

 

[kmoore]

I would argue that a 12ga 00 high velocity buck shot ... within shot gun range would be my definition ! IMHO !

The context was handgun calibers fired in handguns. But I get your point. They have been many shot by a 00 buck that were just injured mainly due to only being hit by 1 or a few pellets and or at range not meant for the shotgun. A full load of 00 buck into a human body is difficult to survive. I know of 1 case that a fleeing robber was hit in the back of his head and died at longer range than normally used for buckshot. About a city block if I remember. That was what bird hunters coined the slang word "magic" pellet. Meaning a single pellet in the head was all that hit the bird and killed it.

 

[Paul B]

"That was what bird hunters coined the slang word "magic" pellet. Meaning a single pellet in the head was all that hit the bird and killed it."

Back around 1964 while stationed at Osan AF B Korea, a few of us went hunting for pheasants near Suwon. Sad to say the pheasants are highly uncooperative so as we slowly went back to the truck to return to base a flock of Snow Geese flew way up yonder overhead. I said to my buddy thatI was gonna take a shot just so I could say I shot at something. I took the shot and one goose locked its wings and glided to a landing. We all ran like hell to get to the bird before the Koreans that were in the area who were also running to collect the bird were going great guns to get there first. It was almost a tie but we got that goose. Mr.Cho, the head houseboy set up a bar b que and we had it for Sunday dinner. Pretty tasty bird.

The "mmgic pellet" had crippled the goose's wing and it had to come down. I admit it that it was one lucky shot.
Paul B.

 

[BearBiologist]

FP or FPE is computed by E = (1/2) x mass x (velocity squared)

 

[Jeepnik]

I always like things like mathematical formulas that crisply, cleanly and repeatedly prove there exactness. The only problem is, reality isn't crisp, clean exact or repeatable.

While "scientists" tend to look down on things that actually happen (they call those anomalies) I haven't found one yet that can explain why things outside of their statistical norms just keep happening.

 

[Ruger Accumulator]

This may be off topic, since the OP asked a technical question. I've never been as enamored with energy levels when it comes to defensive use as some folks are. The problem is the velocity squared part of the formula. Since velocity is so heavily favored, a smaller faster projectile will always appear "better" on paper.

In other words, a BB traveling at a zillion feet per second, will appear to have more power than say a 158 .38 slug traveling at 800 feet per second, which I argue isn't the practical case.

When looking at defensive ammo, I've always favored the simpler momentum formula, which I believe is mass X velocity. I think that gives a more accurate guide as to why heavier slower bullets tend to be more effective than their on paper energy levels would suggest.

45 acp, and 44 special come to mind.