Pennsylvania Firearm Owners Association
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  1. #1
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    Default What force Moves the Slide ?

    ok, So i just got done reading Jerry Kuhnausen principles of the 1911. Big question ? Without assuming what moves the slide after the bullet leaves the barrel and after reading Jerry Kuhnausen principles of the 1911. Don`t you think That the Head of the casing starts to push the slide rearward AFTER the casing Relaxes from being expanded for that millisecond. The casing Expands creates friction in the chamber wall then decides to move backward. I wonder if the extractor is even needed. There is no other force applying pressure to the slide other than the casing itself. So my question is if none of this is true what is creating the movement. ( AK47, gas block + expanded gas + piston = bolt carrier movement )

  2. #2
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    Default Re: What force Moves the Slide ?

    Nope. Every action has an equal and opposite reaction. The bullet has less mass than the gun. Its momentum is overcome first. It is called recoil operated because the barrel and slide, locked together are free to recoil against the recoil spring, until the camming action of the barrel link pulls the lugs out of engagement and stops the barrel but not the slide.

    Blowback operated arms are not locked by anything. Mass and spring pressure delay the rearward motion of the breach for a long enough time to allow pressure to drop to safe levels

    Delayed blowback can use various methods to retard the blowback action. Vented gas filling a piston is one way. This is different than using the vented gas to actually work the action.

  3. #3
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    Default Re: What force Moves the Slide ?

    The case is pushing rearward on the slide as soon as the bullet is fired, the exact same force that is pushing the bullet forward is pushing the slide rearward. Even if the shell is "locked" into the barrel the friction would be carrying the barrel with it. Extractors aren't needed on straight blowback guns (they are there so you can remove unfired rounds) on locked breach guns you have a lot more energy required to operate them.
    NOBODY NEEDS ASSAULT SPEECH

  4. #4
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    Default Re: What force Moves the Slide ?

    I always sleep with my guns when you are gone

  5. #5
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    Smile Re: What force Moves the Slide ?

    Quote Originally Posted by PACO View Post
    ok, So i just got done reading Jerry Kuhnausen principles of the 1911. Big question ? Without assuming what moves the slide after the bullet leaves the barrel and after reading Jerry Kuhnausen principles of the 1911. Don`t you think That the Head of the casing starts to push the slide rearward AFTER the casing Relaxes from being expanded for that millisecond. The casing Expands creates friction in the chamber wall then decides to move backward. I wonder if the extractor is even needed. There is no other force applying pressure to the slide other than the casing itself. So my question is if none of this is true what is creating the movement. ( AK47, gas block + expanded gas + piston = bolt carrier movement )
    Quote Originally Posted by Gunsnwater View Post
    Nope. Every action has an equal and opposite reaction. The bullet has less mass than the gun. Its momentum is overcome first. It is called recoil operated because the barrel and slide, locked together are free to recoil against the recoil spring, until the camming action of the barrel link pulls the lugs out of engagement and stops the barrel but not the slide.

    Blowback operated arms are not locked by anything. Mass and spring pressure delay the rearward motion of the breach for a long enough time to allow pressure to drop to safe levels

    Delayed blowback can use various methods to retard the blowback action. Vented gas filling a piston is one way. This is different than using the vented gas to actually work the action.
    The force of the expanding gases pushes in all directions, but can only go in two. One pushes the bullet out of the barrel, the second pushes the locked barrel/slide in the opposite direction. The casing only provides a seal to contain the pressure. Then as G&W noted once the link pulls the barrel down, down this second force pushes the case out since it is no longer locked in. As he noted this should only happen when the bullet has left the barrel and the pressure curve has dropped significantly. If not you get things like case head separation and other failures that are not good. (this is also why proper head space is important)

  6. #6
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    Default Re: What force Moves the Slide ?

    I will address the issue of the case head pushing the slide back. As gghbi notes the pressure of the gas is equal in all directions. This pressure does flatten the brass to the chamber wall. Any head space not taken up by the unfired cartrage will be filled with stretched brass. The separating force between the breach face and the barrel is halted by the lugs on the top of the barrel and the corresponding slide lugs. This is trying to force them apart. This pressure is not converted into momentum in the 1911. The momentum is the opposite reaction from the acceleration of the projectile. By the time the slide is free to continue rearward without the barrel the pressure is gone because the bullet is gone. If it were not so the case would be ripped in half as the case would still be gripping the chamber walls as hard as it was pushing back on the breach face. That separating force no longer exists. Momentum also known as recoil was imparted at acceleration of the projectile. Yes the acceleration was cause by the burning of the powder, it's increase in volume and resultant pressure, but that is only one of the forces harnessed by JMB in the 1911. Pressure and recoil are two manifestations of energy and are not the same thing nor are they used for the same purpose in this gun.

  7. #7
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    Default Re: What force Moves the Slide ?

    Amazing ingenuity and engineering, isn't it?

  8. #8
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    Default Re: What force Moves the Slide ?

    I always thought it was PFM (Pure Fricken Magic)
    Because Failure Is Not An Option

  9. #9
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    Default Re: What force Moves the Slide ?

    Quote Originally Posted by LMTguy View Post
    I always thought it was PFM (Pure Fricken Magic)
    YES -- PFM courtesy of JMB!!

  10. #10
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    Default Re: What force Moves the Slide ?

    To clarify a few points above, don't confuse acceleration velocity, and momentum. Velocity is the speed at any given time. Acceleration is the change in velocity. momentum is weight x velocity. The acceleration of the barrel/slide assembly rearward stops the moment the bullet leaves the barrel. From there, momentum ( weight x velocity) continues to drive the assembly back, while being resisted by the spring (which is being 'held in place' on the other end by the frame and ultimately your hand, this the recoil you feel). Since the spring is now compressed by the slide (via the force of the expanding gases upon the bullet in one direction, and the case/breach in the other), the gun can utilize the machanical energy now built up in the spring to move forward and overcome the friction inherent in stripping the next round off the magazine and for ing it up the ramp and in the chamber (all more friction).

    If you think about it, you can see that various combinations of bullet weights and powders may not generation enough pressure, or vice versa, too much. Heavy spring rates (or light bullet / powder combo) may shorten a slide cycle to where it doesn't get all the way back and strip the next round, or with a low resistance or worn spring (or heavy bullet, +p load) the slide may move rearward too quickly, affecting accuracy and more importantly, carrying to much momentum and slamming the slide against the rear stop and doing damage to the gun.
    Resistance to tyrants is obedience to God.

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