Sean Smith
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- Dec 28, 2002
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Wait a second, 'knock down power' ???
- Thread starter artherd
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jacketch
Member
"Thanks to, among other things, the inertia of the firearm, the gun doesn't hit you as hard as the bullet hits the target."
Does this mean a human body (much heavier than a pistol) doesn't exhibit inertia?
Does this mean a human body (much heavier than a pistol) doesn't exhibit inertia?
MrAcheson
Member
It actually means the word "inertia" had no business being in that sentence. Sorry Sean, but your explanation is a true mishmash of physics jargon.
The bullet leaves the gun. Momentum conservation means that the gun moves backwards as the bullet moves forwards. However the gun is heavier so it moves slower. The gun now hits the shooter (their hand). Because the gun is moving relatively slowly, the shooter can absorb the recoil impulse safety over large time with small force. The shooter ends up moving even slower than the gun, so they probably won't get hurt.
The bullet hits the target. Lets assume the target wasn't moving and the bullet didn't slow down any. The bullet slows down very fast in the target . This requires a lot of force so the target is going to get hurt. However if the target is the same weight as the shooter, they end up moving the same speed in the opposite direction.
The trick is that the gun lets the shooter absorb the recoil safely which the target doesn't have that luxury so while both get pushed the same the target gets hurt and the shooter doesn't. The real reason the target falls down is that the target is injured and this can cause him/her/it to fall.
Robert J McElwain
Member
This is an interesting thread.
Let me ask a practical question along the lines of "knock down" and inertia and all that stuff.
Let's assume two different people are hit by bullets and in both cases, only soft, non-fatal tissue is hit. One bullet is of moderate caliber from a hunting rifle with moli-coating and solid tip. Not any kind of hollow point.
The other person is hit with a .45 ACP hollow point.
What will be the different effects?
Bob
Let me ask a practical question along the lines of "knock down" and inertia and all that stuff.
Let's assume two different people are hit by bullets and in both cases, only soft, non-fatal tissue is hit. One bullet is of moderate caliber from a hunting rifle with moli-coating and solid tip. Not any kind of hollow point.
The other person is hit with a .45 ACP hollow point.
What will be the different effects?
Bob
bountyhunter
member
YOU FORGOT
That a 200 pound man can be "knocked down" quite easily by a force of a few pounds. It's called BALANCE.
I remember when teaching martial arts, the first thing we would do to a newbie is tell them to stand firm and not move. Then take one finger and push into their chest (center of mass) and they fall over with almost no effort. The point was that you can knock someone down easily if the impact is such that it breaks their balance. In karate, you consciously adjust knee flex and weight distribution to reduce the opponent's ability to break your balance. With a bullet, you can't because it's coming too fast.
We had a cop in San Jose knocked down by the "wimpy" 9mm when he was shot in the hip bone. The bullet stopped instantly so it delivered all of it's energy to his hip bone. The hit was off center and spun him around sending him to the ground. It was no a serious wound, but it definitely was a knockdown.
That a 200 pound man can be "knocked down" quite easily by a force of a few pounds. It's called BALANCE.
I remember when teaching martial arts, the first thing we would do to a newbie is tell them to stand firm and not move. Then take one finger and push into their chest (center of mass) and they fall over with almost no effort. The point was that you can knock someone down easily if the impact is such that it breaks their balance. In karate, you consciously adjust knee flex and weight distribution to reduce the opponent's ability to break your balance. With a bullet, you can't because it's coming too fast.
We had a cop in San Jose knocked down by the "wimpy" 9mm when he was shot in the hip bone. The bullet stopped instantly so it delivered all of it's energy to his hip bone. The hit was off center and spun him around sending him to the ground. It was no a serious wound, but it definitely was a knockdown.
FireInTheHole
Member
Armoredman:
I didnt know there was body armor available beyon level IV... how many rounds of .308 can a 'level five raid vest' take?
Question:
If one had body armor thick enough and sturdy enough withstand (without turning the said person's internals into puree) a center of mass shot from a .50BMG would that shooter get "knocked down"? (roughly 12,000 ft-lbs)
Or even more realistically, a 3" mag slug from a 12 gauge. Many body armors claim they can stop slug loads but would a 1oz slug going 1200fps knock down a person? (roughly 1400-1500ft-lbs)
I didnt know there was body armor available beyon level IV... how many rounds of .308 can a 'level five raid vest' take?
Question:
If one had body armor thick enough and sturdy enough withstand (without turning the said person's internals into puree) a center of mass shot from a .50BMG would that shooter get "knocked down"? (roughly 12,000 ft-lbs)
Or even more realistically, a 3" mag slug from a 12 gauge. Many body armors claim they can stop slug loads but would a 1oz slug going 1200fps knock down a person? (roughly 1400-1500ft-lbs)
bountyhunter
member
Yes, he'd get knocked down. he would also certainly have a ton of broken ribs and massive internal injuries from the shock wave that went through his body. he would also have severe burns as most of the energy of the bullet is transformed into heat as the armor stops it, and that heat is focused on a small area. Cops shot in vests usually get a bruise and a burn.
Feanaro
Member
From what I know most "knockdowns" in a firefight, IE someone falling over, occure because the people in question have had a hole open up in their body. There is not enough energy in the bullet to knock the person down... but the large, thirteen inch hole that they are left with might do it.
Take a 7.62 NATO round and hit someone with it. The bullet does not have enough energy to knock that person over. But the internal injuries would probably do it. But take one of those 700 Nitro bullets, with 100+ pounds of recoil and it could knock someone over. After all, it almost knocks the shooter over.
Take a 7.62 NATO round and hit someone with it. The bullet does not have enough energy to knock that person over. But the internal injuries would probably do it. But take one of those 700 Nitro bullets, with 100+ pounds of recoil and it could knock someone over. After all, it almost knocks the shooter over.
artherd
member
I think it's safe to say that the shooter expierences approximately the same total impulse as that of the person being shot. The latter may expierence it in a shorter interval of time (decelration in 8" vs ~22" of a typical rifle barrel.)
If one were off balance, or otherwise not expecting it, the blunt force from either end of a high powered rifle could knock someone down I suppose.
It is actually much worse if you are wearing a vest, because the bullet will be stoped in less than 2". That's a lot of force per unit time.
Best!
Ben.
If one were off balance, or otherwise not expecting it, the blunt force from either end of a high powered rifle could knock someone down I suppose.
It is actually much worse if you are wearing a vest, because the bullet will be stoped in less than 2". That's a lot of force per unit time.
Best!
Ben.
MrAcheson
Member
Not necessarily, the vest has weight so, like the gun on the other end of the problem, it can help reduce felt impact. The bullet hits the vest which hits you. Also a good vest will spread the impact over a larger area so it won't hurt as much.
Sorry but the great thing about body armor is that flesh is much softer than body armor. Why is this great? As the shockwave propogates through the armor and hits the armor/flesh inferface, the softer flesh will reflect most of the shockwave back through the armor towards the bullet. Its really neat. This is why some more advanced vehicular armors have thin layers of rubber in them. The shockwave hits the rubber and gets reflected back towards the incoming bullet.
corncob
Member
MrAcheson, I'm just curious...
what kind of education/background/practical experience do you have with physics? You sound like an old, classically-trained engineering professor. (I'm in my junior year of engineering school.)
what kind of education/background/practical experience do you have with physics? You sound like an old, classically-trained engineering professor. (I'm in my junior year of engineering school.)
artherd,
As Dr. Rob said, marketing hype. Saw another old add recently that talked about a rounds' "smashing power" or something like that.
Well, I can tell you from personal and recent experience that exact load (Remington Reduced Recoil 1 oz slug) may not knock down a big deer weighing about what the average man weighs.
It will plow through him, though! Add several hundred FPS for a 3" magnum slug. Remington's 3" magnum load is a 1 oz at 1760 fps, giving just over 3000 ft-lbs of energy at the muzzle!
As Dr. Rob said, marketing hype. Saw another old add recently that talked about a rounds' "smashing power" or something like that.
Well, I can tell you from personal and recent experience that exact load (Remington Reduced Recoil 1 oz slug) may not knock down a big deer weighing about what the average man weighs.
It will plow through him, though! Add several hundred FPS for a 3" magnum slug. Remington's 3" magnum load is a 1 oz at 1760 fps, giving just over 3000 ft-lbs of energy at the muzzle!
"This also makes me wonder about "penetration" in gelatin testing. People always seem to want deep penetration - but wouldn't you transfer more energy into the subject if it slowed down quicker, or completely? A 95 grain bullet that goes in a 1000f/s and comes out at 500f/s doesn't transfer as much energy as one that goes in a 1000f/s and doesn't come out... right?"
That may all be true, however, as has been mentioned a number of times in this thread, it seems that knock-down is a myth, so energy transfer doesn't mean a whole lot: especially when we are talking about handgun ammo. So, we resort to plan B: putting holes in vital organs to promote rapid and severe bleeding along with allowing air into the thoracic cavity which will eventually result in a tension pneumothorax and or hemothorax. This is where penetration comes in.
You can hit someone with a baseball bat in the chest and all the energy is disapated. And some serious energy is involved. But, in all likelyhood it isn't going to kill the person. But, putting a hole completely through the chest will, most likely kill them.
I never took physics. I however do know a few things about gunshot wounds. Air in, blood out = good. Two holes are better than one for a couple reasons. Boring a hole clean through the middle of someone's chest is the most reliable method of stopping them with common, handheld weapons.
That may all be true, however, as has been mentioned a number of times in this thread, it seems that knock-down is a myth, so energy transfer doesn't mean a whole lot: especially when we are talking about handgun ammo. So, we resort to plan B: putting holes in vital organs to promote rapid and severe bleeding along with allowing air into the thoracic cavity which will eventually result in a tension pneumothorax and or hemothorax. This is where penetration comes in.
You can hit someone with a baseball bat in the chest and all the energy is disapated. And some serious energy is involved. But, in all likelyhood it isn't going to kill the person. But, putting a hole completely through the chest will, most likely kill them.
I never took physics. I however do know a few things about gunshot wounds. Air in, blood out = good. Two holes are better than one for a couple reasons. Boring a hole clean through the middle of someone's chest is the most reliable method of stopping them with common, handheld weapons.
BluesBear
member
Since the best way of ensuring a "clean through" path would be to use full metal jacketed bullets, you are saying that FMJ would be the best for personal defense?
Compared to what ?
Two holes are better than one.
If you can get the holes bigger, the bigger the better.
Personally, if I had the choice between having two holes and having expansion, I will take the two holes. If there is a way to get both, I will take both. One obvious way to do that is to use a larger caliber from the get go: I took advantage of that from the beginning.
In the example mentioned, we have two 95 grain bullets traveling at 1000 fps. One completely penetrates and leaves at the speed of 500 fps. The other bullet stays within the body. There really isn't enough information to make any real judgement, but it sounds to me like the first bullet would be the better one.
First of all, there is not enough "energy" involved to make it a factor. We don't know if the first bullet disapated all it's energy on something like the sternum and never reached any vital organs. We don't know if the bullet penetrated two inches and petered out. We don't know if the bullet completely fragmented on impact and only did minor flesh damage.
The second bullet gave us complete penetration. That means there are two holes and everything in between those two holes has a hole in it. Everything between those two holes is bleeding.
Expansion is nice. Penetration is essential. Both is better, but if you have to make a choice, penetration is essential, expansion is icing on the cake. It doesn't matter (within reason) how much the bullet expands if it doesn't reach the vitals and put a hole in them.
There is no rocket science here. There are no magical properties involved. People dying from penetrating trauma is nothing new. The way a hangun bullet kills and the way a spear, or knife, or sword kill is the same as it has been since the dawn of time. You have to put a hole through the vital organs. You want bleeding. More bleeding is better. You want air to enter the chest cavity. More air is better.
Two holes are better than one.
If you can get the holes bigger, the bigger the better.
Personally, if I had the choice between having two holes and having expansion, I will take the two holes. If there is a way to get both, I will take both. One obvious way to do that is to use a larger caliber from the get go: I took advantage of that from the beginning.
In the example mentioned, we have two 95 grain bullets traveling at 1000 fps. One completely penetrates and leaves at the speed of 500 fps. The other bullet stays within the body. There really isn't enough information to make any real judgement, but it sounds to me like the first bullet would be the better one.
First of all, there is not enough "energy" involved to make it a factor. We don't know if the first bullet disapated all it's energy on something like the sternum and never reached any vital organs. We don't know if the bullet penetrated two inches and petered out. We don't know if the bullet completely fragmented on impact and only did minor flesh damage.
The second bullet gave us complete penetration. That means there are two holes and everything in between those two holes has a hole in it. Everything between those two holes is bleeding.
Expansion is nice. Penetration is essential. Both is better, but if you have to make a choice, penetration is essential, expansion is icing on the cake. It doesn't matter (within reason) how much the bullet expands if it doesn't reach the vitals and put a hole in them.
There is no rocket science here. There are no magical properties involved. People dying from penetrating trauma is nothing new. The way a hangun bullet kills and the way a spear, or knife, or sword kill is the same as it has been since the dawn of time. You have to put a hole through the vital organs. You want bleeding. More bleeding is better. You want air to enter the chest cavity. More air is better.
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