4 ms·

All good points except for the last one even if you could even theoretically develop practical armor that could stop cal. 50 round it would still be able to kil

by qaq 9y ago

All good points except for the last one even if you could even theoretically develop practical armor that could stop cal. 50 round it would still be able to kill a person through the impact force damaging internal organs.

CydeWeys 9y ago
Not true at all. If the person firing the round can survive the momentum imparted into their shoulder from the rifle, then the person on the receiving end can survive it if they're wearing armor that spreads out the imparted momentum similarly. Basic Newton's Third Law. Also, there are .50 BMG handguns (and no, I'm not mistakenly referring to .50 AE, I mean .50 BMG). They are stupidly impractical, but they exist. You're making this out to be some mythical projectile when it's really just a bigger bullet. It's not like getting hit by a tank shell. The real flaw with this scenario is that full body armor required to stop .50 BMG would be so bulky and heavy that you wouldn't be able to move. The imparted momentum isn't the problem, it's stopping the penetration of the round. It's also worth pointing out that this conversation is pointlessly academic, as .50 BMG has not been used in a murder once. Ever. In the entire history of the United States. Out of over one million gun murders total. It's ridiculously impractical for that purpose.
- maxerickson 9y ago
  Large rifles work better than pushing all the recoil into the shooter. https://www.americanrifleman.org/articles/2016/4/29/the-barrett-model-82a1-rifle/ https://www.americanrifleman.org/articles/2016/4/29/the-barr... Pretty hard to put a muzzle brake on your body armor.
- j9461701 9y ago
  The killer is not the momentum, but the impulse. Let's do some simple kinematics: The M82 has a barrel length of 20 inches (51 cm, .051 meters) and fires a 45 gram bullet that, at the end of that time, is going 900 m/s. Meaning the bullet goes from having zero momentum to 41 Newton-seconds in 1.13 milliseconds. Meaning the shooter feels over that 1.13 millisecond period of ~36,000 Newtons of force on his shoulder. The person getting shot has to make that bullet go from 900 m/s to 0, but he has to do it over say 2 inches of distance or his organs start getting smushed. Meaning he's experiencing, over that 110 microsecond period, ~360,000 Netwons of force. The exact same momentum, but in the shooter's case it's like getting punched and in the shootee's case it's like getting your torso gummed on by a T-rex. This is why going from 0 to 100 in a car can either be no big deal (if done over 60 seconds) or kill you six ways from sunday (if done in a few milliseconds when you crash into a wall or something). We're also not getting into the power of a good muzzle break or the weight of the rifle itself, both of which considerably reduce the felt impulse by the shooter. You can look up people rapid-firing 50 cal rifles from the hip on youtube for an illustration of just how much you can tame the recoil of these guns.
  - CydeWeys 9y ago
    A typical body armor plate has much more surface area in contact with the body than a rifle butt does though -- we're talking roughly an entire square foot. Said body armor plate, if it's to stop a .50 BMG round, also will be thick enough to weigh as much as an M82. This makes up for the fact that the acceleration happens over a reduced distance. Also keep in mind that a rifle needs to be comfortable enough for many repeated shots, while body armor only needs to be survivable. Note that you're at ~80 pounds from wearing just two plates to protect most of your chest and back; you'll collapse under the weight by the time you've armored your entire body.
    - j9461701 9y ago
      For point of reference, shotgun slugs can be stopped by modern armor. It still cracks people's ribs through sheer impulse. A 50 BMG has 5 times the kinetic energy and 3 times the momentum of that. It's simply not enough to stop the bullet at these kinds of impulses, you need something to distribute the force over time as well as space. Cars use crumple zones for this purpose - the time it takes the front to deform is extra seconds over which the momentum change takes place, thereby decreasing the impulse. Even if we could develop some sort of powered armor that let you carry absurd amounts of armour I don't see how you could really solve this problem. The suit is still going to push back into the wearer's body with the same impulse, and crack bones when it does. Ultimately, the truth is human beings are just too squishy. #BringOnTheRobots
      - adrianN 9y ago
        If we allow for powered armor I can imagine armor with appropriate crumple zones. But I guess with powered armor you also get to carry ridiculously huge guns...
      - CydeWeys 9y ago
        Shotgun slugs are a lot less penetrative than .50 BMG though; they're proportionally heavier and travel slower. 12 gauge is .73 inches. You need significantly more thickness of armor just to stop the .50 BMG at all, by which point you've added so much more mass that you've gone much of the towards solving the higher impulse as well.
- lb1lf 9y ago
  Oh, I just figured 50cal would leave sufficient overkill factor to cover all situations - after all, I think it would be unfair to require police officers to show lots more restraint using their firearms if they didn't have armour capable of saving them should the situation escalate; after all - if I was given PPE at work which would be sufficient to get me out of 70% of incidents alive, my first (and last!) question would be "Fine, what about the 30% which'll kill me?"
  - Silhouette 9y ago
    If this incident began with a planned approach by the police, on the assumption that they might be facing someone violent and armed, one of the first questions should surely be why any officers outside the building were so exposed that they were concerned about being suddenly shot by the suspect. Do these officers not arrive equipped with body armour, shields, armoured vehicles and the like in a situation like this?

by qaq 9y ago

CydeWeys 9y ago

Not true at all. If the person firing the round can survive the momentum imparted into their shoulder from the rifle, then the person on the receiving end can survive it if they're wearing armor that spreads out the imparted momentum similarly. Basic Newton's Third Law. Also, there are .50 BMG handguns (and no, I'm not mistakenly referring to .50 AE, I mean .50 BMG). They are stupidly impractical, but they exist. You're making this out to be some mythical projectile when it's really just a bigger bullet. It's not like getting hit by a tank shell. The real flaw with this scenario is that full body armor required to stop .50 BMG would be so bulky and heavy that you wouldn't be able to move. The imparted momentum isn't the problem, it's stopping the penetration of the round. It's also worth pointing out that this conversation is pointlessly academic, as .50 BMG has not been used in a murder once. Ever. In the entire history of the United States. Out of over one million gun murders total. It's ridiculously impractical for that purpose.

maxerickson 9y ago
Large rifles work better than pushing all the recoil into the shooter. https://www.americanrifleman.org/articles/2016/4/29/the-barrett-model-82a1-rifle/ https://www.americanrifleman.org/articles/2016/4/29/the-barr... Pretty hard to put a muzzle brake on your body armor.
j9461701 9y ago
The killer is not the momentum, but the impulse. Let's do some simple kinematics: The M82 has a barrel length of 20 inches (51 cm, .051 meters) and fires a 45 gram bullet that, at the end of that time, is going 900 m/s. Meaning the bullet goes from having zero momentum to 41 Newton-seconds in 1.13 milliseconds. Meaning the shooter feels over that 1.13 millisecond period of ~36,000 Newtons of force on his shoulder. The person getting shot has to make that bullet go from 900 m/s to 0, but he has to do it over say 2 inches of distance or his organs start getting smushed. Meaning he's experiencing, over that 110 microsecond period, ~360,000 Netwons of force. The exact same momentum, but in the shooter's case it's like getting punched and in the shootee's case it's like getting your torso gummed on by a T-rex. This is why going from 0 to 100 in a car can either be no big deal (if done over 60 seconds) or kill you six ways from sunday (if done in a few milliseconds when you crash into a wall or something). We're also not getting into the power of a good muzzle break or the weight of the rifle itself, both of which considerably reduce the felt impulse by the shooter. You can look up people rapid-firing 50 cal rifles from the hip on youtube for an illustration of just how much you can tame the recoil of these guns.
- CydeWeys 9y ago
  A typical body armor plate has much more surface area in contact with the body than a rifle butt does though -- we're talking roughly an entire square foot. Said body armor plate, if it's to stop a .50 BMG round, also will be thick enough to weigh as much as an M82. This makes up for the fact that the acceleration happens over a reduced distance. Also keep in mind that a rifle needs to be comfortable enough for many repeated shots, while body armor only needs to be survivable. Note that you're at ~80 pounds from wearing just two plates to protect most of your chest and back; you'll collapse under the weight by the time you've armored your entire body.
  - j9461701 9y ago
    For point of reference, shotgun slugs can be stopped by modern armor. It still cracks people's ribs through sheer impulse. A 50 BMG has 5 times the kinetic energy and 3 times the momentum of that. It's simply not enough to stop the bullet at these kinds of impulses, you need something to distribute the force over time as well as space. Cars use crumple zones for this purpose - the time it takes the front to deform is extra seconds over which the momentum change takes place, thereby decreasing the impulse. Even if we could develop some sort of powered armor that let you carry absurd amounts of armour I don't see how you could really solve this problem. The suit is still going to push back into the wearer's body with the same impulse, and crack bones when it does. Ultimately, the truth is human beings are just too squishy. #BringOnTheRobots
    - adrianN 9y ago
      If we allow for powered armor I can imagine armor with appropriate crumple zones. But I guess with powered armor you also get to carry ridiculously huge guns...
    - CydeWeys 9y ago
      Shotgun slugs are a lot less penetrative than .50 BMG though; they're proportionally heavier and travel slower. 12 gauge is .73 inches. You need significantly more thickness of armor just to stop the .50 BMG at all, by which point you've added so much more mass that you've gone much of the towards solving the higher impulse as well.
lb1lf 9y ago
Oh, I just figured 50cal would leave sufficient overkill factor to cover all situations - after all, I think it would be unfair to require police officers to show lots more restraint using their firearms if they didn't have armour capable of saving them should the situation escalate; after all - if I was given PPE at work which would be sufficient to get me out of 70% of incidents alive, my first (and last!) question would be "Fine, what about the 30% which'll kill me?"
- Silhouette 9y ago
  If this incident began with a planned approach by the police, on the assumption that they might be facing someone violent and armed, one of the first questions should surely be why any officers outside the building were so exposed that they were concerned about being suddenly shot by the suspect. Do these officers not arrive equipped with body armour, shields, armoured vehicles and the like in a situation like this?