3 ms·

>Shotgun slugs are a lot less penetrative than .50 BMG though; they're proportionally heavier and travel slower. What does the word "proportionally" mean in th

>Shotgun slugs are a lot less penetrative than .50 BMG though; they're proportionally heavier and travel slower. What does the word "proportionally" mean in this sentence? Because factually, the slug is about half the weight of the BMG round. >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. You're looking at elephant-stomping-on-you levels of force, and you're trying to say it'll be mitigated somewhat because you have 5 pounds of steel on your chest rather than 2 pounds. You will be a person salsa even if you strapped a kitchen stove to yourself. You don't seem to be understanding the magnitude of the forces involved.

trhway 9y ago
>You're looking at elephant-stomping-on-you levels of force, and you're trying to say it'll be mitigated somewhat because you have 5 pounds of steel on your chest rather than 2 pounds. You will be a person salsa even if you strapped a kitchen stove to yourself. the momentum conservation means that the 5 pound of steel would be moving with the speed of 18m/s after full momentum transfer from the 45g bullet hitting it at 900m/s. 5lb at 18m/s - is like somebody would hit you with a frying pan. While painful and dangerous if say into the head, it is still much less so than getting the bullet directly. Even better result would be with a 25 lb steel plate - just 3.6m/s - like somebody would shove an office/kitchen table at you. Elephant leg say weights 250kg - that would mean that if you have an elephant leg as an armor in front of you, after being hit by a 0.50 bullet with full momentum transfer the leg will be moving at the speed of 0.18m/s - you can just slowly step away from it. >You don't seem to be understanding the magnitude of the forces involved. please enlighten us and correct my calculations above.
- j9461701 9y ago
  I don't mean to be rude, but did you not understand what I wrote above? >the momentum conservation means that the 5 pound of steel would be moving with the speed of 18m/s after full momentum transfer from the 45g bullet hitting it at 900m/s. 5lb at 18m/s - is like somebody would hit you with a frying pan. The change in momentum over time is what matters, not the momentum itself. As I said above, think of a car. The momentum change on your body from going from 0 to 100 mph is a slight push on your chest....if you spread that momentum change over 60 seconds of steady acceleration. The exact same momentum change, if done over a few milliseconds from say smashing into a brick wall, is probably going to kill you. I mean this isn't rocket science, it's literally high school physics. >please enlighten us and correct my calculations above. I...did the math already? Did you not read it? The momentum change over the distance of 2 inches produces a force of about 360,000 Newton - a 6000 kg elephant just standing on you would produce "only" 60,000 newtons. He needs to be actively trying to stomp your daylights in to get the kind of forces we're talking about. 50 cal is the kind of round that you hit someone in the torso and their arms fly off. It was built to kill vehicles and planes, for people it is absurd overkill.
  - trhway 9y ago
    >The momentum change over the distance of 2 inches produces a force of about 360,000 Newton you're right that the force will be huge, and you're dead wrong about the force effect. lets say we stop the bullet over the distance of 1cm instead of 2 inches - the stopping force to act upon bullet would be even bigger - 1.8M Newtons (30 elephants!). The same value force will be acting upon our 5lb armor plate. This force will be acting until the bullet stops, ie. for about 0.02 milliseconds. During that time the force would accelerate the armor plate to the speed of 16m/s and the armor plate would travel less than 1mm - only starting to compress the padding under the armor plate. So, 0.02 milliseconds after the bullet impact we have a stopped bullet and the armor plate moving with the speed of 16m/s through the first millimeter of the padding - the situation is no different than being hit by a frying pan.
    - j9461701 9y ago
      >lets say we stop the bullet over the distance of 1cm instead of 2 inches - the stopping force to act upon bullet would be even bigger - 1.8M Newtons (30 elephants!). The same value force will be acting upon our 5lb armor plate. This force will be acting until the bullet stops, ie. for about 0.02 milliseconds. During that time the force would accelerate the armor plate to the speed of 16m/s and the armor plate would travel less than 1mm - only starting to compress the padding under the armor plate. So, 0.02 milliseconds after the bullet impact we have a stopped bullet and the armor plate moving with the speed of 16m/s through the first millimeter of the padding - the situation is no different than being hit by a frying pan. That's not how impulse propagates. The force carries through the plate, into the person, and does its damage as a compressive wave. Think about seatbelts in a car during a high speed crash - they don't often penetrate the torso of people, but they can and do pop organs through compressive effects if they're worn too high. Yet calculate the momentum of the seat belt at 100 mph and you'll find it's tiny, like a light slap. But let's assume your analysis is true. Why then does a shotgun slug, with considerably less momentum than the .50 cal and even a frying pan, crack ribs through armor? Why can I put a piece of AR500 steel in front of a watermellow, hit the steel with a .308, and have the watermellon explode despite nothing getting through? But I'm done. I've explained this same concept 5 different times, and I'm still having to cover basic physics with people too proud to admit their layman's interpretation is wrong. If you think you could survive a .50 with armor, you're welcome to go buy a 1 inch plate from shootsteel.com and an M82 and test if out yourself. Remove one more prideful fool from the gene pool.
- freedomben 9y ago
  See this is why I come to HN. For nerdy interesting analysis that's relevant. Much better than 90% of the comments that are fools who find no pleasure in understanding but delight in airing their own opinions. This is no better than a political article as far as bringing out the dark side of people.
- maxerickson 9y ago
  5 pounds ain't enough steel to achieve full momentum transfer. https://www.youtube.com/watch?v=chZZp-ALV6o https://www.youtube.com/watch?v=chZZp-ALV6o (I looked up the high strength steel armor plates; they do weigh about 5 pounds) This big chunk of steel stops the bullet: https://www.youtube.com/watch?v=BrfskAfPB5s https://www.youtube.com/watch?v=BrfskAfPB5s Bit of a kick though and it pretty obviously isn't practical to strap something of similar strength to your body.

trhway 9y ago

>You're looking at elephant-stomping-on-you levels of force, and you're trying to say it'll be mitigated somewhat because you have 5 pounds of steel on your chest rather than 2 pounds. You will be a person salsa even if you strapped a kitchen stove to yourself. the momentum conservation means that the 5 pound of steel would be moving with the speed of 18m/s after full momentum transfer from the 45g bullet hitting it at 900m/s. 5lb at 18m/s - is like somebody would hit you with a frying pan. While painful and dangerous if say into the head, it is still much less so than getting the bullet directly. Even better result would be with a 25 lb steel plate - just 3.6m/s - like somebody would shove an office/kitchen table at you. Elephant leg say weights 250kg - that would mean that if you have an elephant leg as an armor in front of you, after being hit by a 0.50 bullet with full momentum transfer the leg will be moving at the speed of 0.18m/s - you can just slowly step away from it. >You don't seem to be understanding the magnitude of the forces involved. please enlighten us and correct my calculations above.

j9461701 9y ago
I don't mean to be rude, but did you not understand what I wrote above? >the momentum conservation means that the 5 pound of steel would be moving with the speed of 18m/s after full momentum transfer from the 45g bullet hitting it at 900m/s. 5lb at 18m/s - is like somebody would hit you with a frying pan. The change in momentum over time is what matters, not the momentum itself. As I said above, think of a car. The momentum change on your body from going from 0 to 100 mph is a slight push on your chest....if you spread that momentum change over 60 seconds of steady acceleration. The exact same momentum change, if done over a few milliseconds from say smashing into a brick wall, is probably going to kill you. I mean this isn't rocket science, it's literally high school physics. >please enlighten us and correct my calculations above. I...did the math already? Did you not read it? The momentum change over the distance of 2 inches produces a force of about 360,000 Newton - a 6000 kg elephant just standing on you would produce "only" 60,000 newtons. He needs to be actively trying to stomp your daylights in to get the kind of forces we're talking about. 50 cal is the kind of round that you hit someone in the torso and their arms fly off. It was built to kill vehicles and planes, for people it is absurd overkill.
- trhway 9y ago
  >The momentum change over the distance of 2 inches produces a force of about 360,000 Newton you're right that the force will be huge, and you're dead wrong about the force effect. lets say we stop the bullet over the distance of 1cm instead of 2 inches - the stopping force to act upon bullet would be even bigger - 1.8M Newtons (30 elephants!). The same value force will be acting upon our 5lb armor plate. This force will be acting until the bullet stops, ie. for about 0.02 milliseconds. During that time the force would accelerate the armor plate to the speed of 16m/s and the armor plate would travel less than 1mm - only starting to compress the padding under the armor plate. So, 0.02 milliseconds after the bullet impact we have a stopped bullet and the armor plate moving with the speed of 16m/s through the first millimeter of the padding - the situation is no different than being hit by a frying pan.
  - j9461701 9y ago
    >lets say we stop the bullet over the distance of 1cm instead of 2 inches - the stopping force to act upon bullet would be even bigger - 1.8M Newtons (30 elephants!). The same value force will be acting upon our 5lb armor plate. This force will be acting until the bullet stops, ie. for about 0.02 milliseconds. During that time the force would accelerate the armor plate to the speed of 16m/s and the armor plate would travel less than 1mm - only starting to compress the padding under the armor plate. So, 0.02 milliseconds after the bullet impact we have a stopped bullet and the armor plate moving with the speed of 16m/s through the first millimeter of the padding - the situation is no different than being hit by a frying pan. That's not how impulse propagates. The force carries through the plate, into the person, and does its damage as a compressive wave. Think about seatbelts in a car during a high speed crash - they don't often penetrate the torso of people, but they can and do pop organs through compressive effects if they're worn too high. Yet calculate the momentum of the seat belt at 100 mph and you'll find it's tiny, like a light slap. But let's assume your analysis is true. Why then does a shotgun slug, with considerably less momentum than the .50 cal and even a frying pan, crack ribs through armor? Why can I put a piece of AR500 steel in front of a watermellow, hit the steel with a .308, and have the watermellon explode despite nothing getting through? But I'm done. I've explained this same concept 5 different times, and I'm still having to cover basic physics with people too proud to admit their layman's interpretation is wrong. If you think you could survive a .50 with armor, you're welcome to go buy a 1 inch plate from shootsteel.com and an M82 and test if out yourself. Remove one more prideful fool from the gene pool.
freedomben 9y ago
See this is why I come to HN. For nerdy interesting analysis that's relevant. Much better than 90% of the comments that are fools who find no pleasure in understanding but delight in airing their own opinions. This is no better than a political article as far as bringing out the dark side of people.
maxerickson 9y ago
5 pounds ain't enough steel to achieve full momentum transfer. https://www.youtube.com/watch?v=chZZp-ALV6o https://www.youtube.com/watch?v=chZZp-ALV6o (I looked up the high strength steel armor plates; they do weigh about 5 pounds) This big chunk of steel stops the bullet: https://www.youtube.com/watch?v=BrfskAfPB5s https://www.youtube.com/watch?v=BrfskAfPB5s Bit of a kick though and it pretty obviously isn't practical to strap something of similar strength to your body.