List of Common Misconceptions

Discussion in 'Off Topic' started by Ed Hardy, Feb 7, 2012.

  1. Varjak

    Varjak Mobile Deity

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    I hesitate to get in the middle of this; but I am confused a bit by the difference b/t muzzle velocity and the 'speed of the bullet.'

    Kinetic energy is equal to 1/2*M*V[squared]. Velocity is weighted more than the mass (of the projectile). All else being equal (like leaving out fragmenting projectiles), isn't the KE the important factor in 'stopping power?'

    Also, I believe most major police departments train officer to 'shoot to kill.' Some argue it shouldn't be that way; but it's awfully hard to try and disable a violent criminal.
     
  2. Adama D. Brown

    Adama D. Brown Brighthand Reviewer

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    Not muzzle velocity, muzzle energy. Muzzle energy is, basically, the speed of the bullet combined with it's weight. For instance, a 100 grain bullet traveling at 1000 feet per second will carry 302 joules of kinetic energy. Double the weight of the bullet, 200 grains at 1000 fps, and the energy doubles to 604 joules. However it doesn't scale that when you mess with velocity; a 100 grain bullet at 2,000 fps will carry four times the energy, 1208 joules. Whenever you double the speed of an impact, you quadruple the energy. That goes for both bullets and things like car wrecks.

    You're correct. "Shoot to disable" is kind of a myth in and of itself--even a shot to the arm or leg can easily be fatal if it hits a main artery.

    You know, between me, hal, and weegie, I'm starting to think we need our own BH OT "firearms geeks" thread.
     
  3. hal

    hal itchy and cold feet hal

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    Well, shoot. I'm an engineer, I'm a nerd, I'm a geek, I'm a freak. BTW I could do a song out of this :D Perhaps that's the reason I would never be considered to join that kind of show. Or any other kind of show either. I can easily turn many subjects into non-fun :rolleyes:

    You know, if you don't have a specific goal in mind, it turns out to be boring and sterile. Pointless, they say. A specific goal, like being a sniper, a match shooter, olympic contestant, long range hunter, etc. I mean, very specific reasons to study in-depth the behavior of specific loads. Otherwise, it's better to leave the ballistics tech to somebody else and purchase the charts instead of trying to make them or correct them.

    IME the actual bad side of gun clubs is that for some obscure reason they attract rednecks with an attitude problem. Don't get me wrong, I got nothing against them, but it seems that many kinda feel socially re-paired when bearing a loaded weapon. It's like a social vendetta trying to happen on somebody. Of course there are the mouths, mostly dudes that have something to prove. OK, I carry ear muffles anyway ;)

    Of course the entertainment value of an engineering point of view is minimal, to none :D But no matter how enjoying can this show be, I can't help comparing their "tests" with what I have seen at school and at different jobs. BTW, at a point in my career, I acted labs master for a company. I was metrologist and process tests lab caretaker. I was responsible for all the measuring instruments used within the company's premises, and was responsible of the supervision of all the test & evaluation methods throughout the process. Quality stuff, you know. So next I see a couple of dudes something in between the Hell's Angels and the Afrika Korps trying to challenge this or that assertion, with the same "tech" that a junkyard can provide. Or a garbage dump. No scientific rigor. BTW the one with the martial artist trying to stop the arrows was indeed hilarious.

    In a sideline, lemme point out that there's a couple of factors about the MythBusters that I do consider good. One, they jumpstart out of no knowledge. Now this is a core feature in order to keep on learning throughout life and career, be able to say "I don't know rip about this", and next get oneself soaked into a subject. The bad thing is that the MythBusters don't get soaked, but just mild damped. Anyway, the former is a true keeper. Second, they do something that's pretty good in order to get things done: start with a practical approach. Sadly, they don't do practical, but empirical. Anyway, the former is also a true keeper.

    :D ;)

    Essentially, Varjak, you hit it square in the head. The KE is one of the "what it's all about" when delivering a projectile against a target (the other being the expected projectile's behavior on impact). The stopping power is in a nutshell the mixed effect of the KE and the bullet impact mechanics (how it behaves when hitting the target, does it penetrate, does it also expand, etc.). The stopping power can be described as the global dissipation (and related effects) of the KE on the target. But there has to be a KE in the first place :)

    Right. But an important clarification is that it's named muzzle energy cause it's measured right at the muzzle. All the factors involved in launching the round, such as powder quality, chamber pressure, shell/chamber clearance, etc., are all rounded up in the measure of the energy of the bullet as it leaves the barrel (at the muzzle, hence the name). Said muzzle energy is the maximum energy comprised by the shot. This energy will decrease through distance by means of friction with air (or any other media such as water), gravity pull and several other factors in the environment. Muzzle energy is one of the prime factors in measuring the effect of the shot.

    Totally right. Not even when speaking of non-lethal ammunition, can a law enforcement officer ensure that a suspect will survive. The "plastic" ammunition used in Israel has opened suspects from the breastbone to the pelvis (geez), and the rubber ammo used in France for riots has killed more than one due to severe head trauma. Anyway, such as weegie points out, there must be places where as much as reality is gonna put it in the face of the officer, they're not gonna put it in their manuals. Brave guys I say.

    :D :D :D
    And perhaps we should.
     
  4. hal

    hal itchy and cold feet hal

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    Common misconception: actually an intended one. Mexican folk music groups known as Mariachis depict the countryside Mexican life.
     
  5. Varjak

    Varjak Mobile Deity

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    Ahh... So I guess we're all pretty much on the same page.

    Sorry I misread what you wrote. In this instance, ME = KE.
     
  6. hal

    hal itchy and cold feet hal

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    Not quite; ME = PE + KE
    The mechanical energy not only encompasses the kinetic energy phenomena, but also the potential energy. And, the lesser the one, the greater the other.

    In a gunshot, there are two considerations regarding potential energy. One, and the reason why this energy is not usually mentioned in ballistics calculations, is that all the potential energy is (literally) encased in all the events that lead to the bullet being put in movement. The shooter cocking the gun, the energy held in the primer, the energy held in the powder, and then all this energy getting collected (losses here and there of course), and then used to put the bullet in movement. Then under this point of view all that's left of the ME equation is KE.

    The other consideration, a purely physical one, tries to focus on the mechanics of the bullet as it leaves the muzzle, considering that all ME = muzzle energy, then there's a PE to calculate within, but it will essentially deliver nothing but negative results (meaning of a (-) value) cause all calculations invariable deliver the aforementioned decrease of energy from the muzzle to the target. The purpose of this second consideration usually involves the measure of said energy loss in order to re-calculate caliber features and minimize said loss in order to favor an improved ballistic effect.

    EDIT: you posted "in this instance", ME = KE. Okay, yes, so I apologize if these descriptions are out of place.
     
  7. Varjak

    Varjak Mobile Deity

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    Yes, isn't PE potential energy? You can't add those.
     
  8. jigwashere

    jigwashere Mobile Deity

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    Forget Extinct: The Brontosaurus Never Even Existed

    tw1017-bronto-to-go.jpeg
     
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