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Thread: Recoil

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  1. #21
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    Quote Originally Posted by Hawkmoon
    Do you honestly believe that, just because you read it on the Internet, it's correct?

    Gotttriplets said it right. The law is conservation of energy. I was a physics major. Never heard of any "conservation of momentum" law. I suspect it's something like new math -- a creation of teachers who can't figure out how to explain the real thing, so they come up with their own explanations ... which are usually badly flawed.
    Can you get your tuition refunded? Here is what NASA says about your non-existant law.
    http://www.lerc.nasa.gov/WWW/K-12/airplane/conmo.html

    The conservation of momentum is a fundamental concept of physics along with the conservation of energy and the conservation of mass.

    I use the links because it's easy to understand for those who haven't had to sit through the classroom.

    I have a ** and MS in Chem Eng. and only took 6 semesters of physics. That was in the 70's but I think physics is still the same. Yes, we learned Newton's Laws. Conservation of momentum is covered in the third law.

    You don't believe in opposite and equal actions?

    You have to define a system to look at energy, or work, or momentum. The entire gun and shooter make up the system. BTW, this is why a shooter can indeed limp wrist (or break wrist which I call it).

    Tuner's expalantion does not in any way contradict the conservation of momentum, IMO, if we add the appropriate masses, velocities, and forces, it confirms it.
    Last edited by Kruzr; 7th September 2006 at 12:34.


  2. #22
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    Conservation of...

    Conservation of Momentum is a refurbished, renewed, rewritten, lemon-scented, fluffed and buffed...and politically correct version of Newton's Laws of Motion. It also sounds more intellectual when you're teaching a class at a prestigious university than saying Laws of Motion...whether you actually get the students to understand it or not.

    The ones that we're concerned with here are the first and the third.

    1. Objects in motion tend to remain in motion. Objects at rest tend to remain at rest. Both will do what Sir Issac tells'em to do unless and until a force is exerted that is sufficient to either overcome the resistance of the first, and put it in motion...or the momentum/kinetic energy of the second,
    and bring it to a halt.

    3. For every action, there must be an equal and opposite reaction.

    Refer back to Rule 1. All objects have mass. Mass requires that a force be exerted against it in order for it to either move...or stop moving. That force must be sufficient to overcome whichever one that you're exerting that force against...or one will keep moving, albeit at a slower pace...and the other won't budge.

    If the force exerted against the object at rest is equal to its resistance, you have equilibrium. Nothing happens. If the force exerted on the moving object is equal to its conserved momentum/kinetic energy, everything will
    stop moving...and you create a state of equilibrium from a state of motion.

    Simple...Right? Mass requires force in order to go from a state of equilibrium to a state of motion.

    Equal and opposite reaction. In gunspeak, that's recoil. Before recoil can occur, there must be a force vector that acts on both bullet and breechblock...or slide...at the same time, with sufficient energy to move them. That vector can push them from the inside, or it can pull them from the outside. Neither the bullet nor the breechblock/slide know the difference.
    This occurs, whether or not the barrel is locked to the slide, and whether or not either is locked to the receiver. Weld the barrel to the slide and the slide to the frame and fire the gun...and it will still recoil. The slide just won't cycle.

    Bullet and breechblock/slide are at rest...in a state of equilibrium...until the powder ignites. The powder creates the force vector necessary to impart motion in both. Apply force to either one alone, and only that part will move.
    Pulling the bullet though the barrel won't cause the slide to cycle any more than yanking the slide will cause the bullet to accelerate to 830 fps in 4.2 inches of rifling.

    If you could conceivably yank the slide hard enough...and the extractor could hang on to the case rim under that level of G force...you could get the bullet to stand still, and APPEAR to move...but that's a whole 'nother cigar. It's like the phenomenon of bullets "Jumping the Crimp" in heavy revolver loads. The gun recoils away from the bullet. The bullet obeys Newton and fights to stay put. The cartridge rims aid and abet.

    Mass requires force to make it move. Recoil and acceleration are not forces.
    They are the results of force applied.

  3. #23
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    Some threads should have a martini symbol attached which would warn, "Don't read without fortification!"

    Kruzer have one on me. You haven't forgotten anything that I can see.

  4. #24
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    Quote Originally Posted by Stone Knife
    Kruzer have one on me. You haven't forgotten anything that I can see.
    That'd pretty well sum it up, I'd say...and neither has Hawk. They just went to different schools and had different perfessers. Makes me feel plumb illiterate.
    I had two semesters of applied physics that was part of an M.E.T. program that I didn't finish...due to circumstances beyond my control. I do, however, remember enough of it to know that the slide doesn't cycle just because the bullet goes through the barrel.


  5. #25
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    In a blowback, the bullet goes one way and the slide goes in the other and the barrel stands still...and the expanding gasses move both.
    Which is why the HK P7 will still cycle without the extractor. But most are convinced it's some uber secret technology that HK built into the gun.

    On a side note, this is why grip angle and bore height make a difference in the "felt" recoil of a weapon. The amount of force expended is the same assuming the same bullet loading and weight of the components. But you are changing the fulcrum and the length of the lever.

    And I thought I'd never use that stuff after high school?!
    "The 1911 was the design, given by God to us through John M. Browning, that represents the epitome of what a killing tool needs to be. It was true in 1911 and it's true now." - Col. Robert Coates commanding, U.S. Marine Corp Special Operations Command Detachment 1 (DET 1)

  6. #26
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    Quote Originally Posted by garrettwc
    Which is why the HK P7 will still cycle without the extractor.
    Don't look now...but I've seen 1911s do the same thing. It's a matter of timing. If the breech opens before the residual pressures have dropped far enough, they'll blow the case right out of the barrel...and the pistol will function surprisingly well. However...
    if the locked breech/recoil operated pistol does that little trick, it's not functioning properly.
    Last edited by 1911Tuner; 8th September 2006 at 04:40.


  7. #27
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    While the momentum of a cannon firing a projectile must be conserved, we are talking about components of a system, not the entire system.
    Notice that conservation of momentum applies to "isolated systems".
    Conservation of momentum is why a bullet cannot knock someone off their feet.
    It would have to have knocked the shooter off thier feet when fired.
    A bullet in a barrel is not an isloated system and you cannot apply conservation of momentum to a portion of the system.
    It applies to the entire gun and even the weight of the hand and arm holding the gun.

    Pressure drives the bullet one way and the gun the other. If there was no friction and springs involved it would be simple.
    The bullet/barrel friction pulls the barrel forward even as the barrel and slide are starting to recoil back. When the bullet exits the forward friction is gone and the barrel can unlock. Handy little delay there.

  8. #28
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    re:

    Brickey! Yes! YES!

  9. #29
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    Quote Originally Posted by Kruzr
    You don't believe in opposite and equal actions?
    I beg your pardon?

    Quote Originally Posted by Hawkmoon
    From high school physics class: "For every action, there is an equal and opposite reaction"

    Bullet <== BANG! ==> Slide
    The energy of the explosion in the cartridge impinges on both the bullet and the casing, transferring equal amounts of energy in all directions. Since the energy acting outward (radially) from the casing is restricted by the barrel/chamber, the bulk of the energy is transferred into pushing the bullet forward down the barrel, and the now-empty casing in the opposite direction. However, the casing is in intimate contact with the breech face of the slide, so the energy transferred in the rearward direction is immediately transferred through the casing into the slide, causing the slide to begin to retract as the bullet begins to move down the barrel. Because of the disparity between the mass of the bullet vs. the mass of the slide+casing combination, the bullet accelerates to a much higher velocity than the slide.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside

  10. #30
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    The physics law is "conservation of energy" not momentum. Conservation of momentum is a by-product of the conservation of energy.
    John Caradimas SV1CEC
    The M1911 Pistols Organization
    http://www.m1911.org

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