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Thread: Explanation of the operation of EGW Firing Pin Stop

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  1. #21
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    Quote Originally Posted by Bob_W
    I have been lucky enough to not have a bullet stuck in a barrel but if the barrel stays together when a second bullet is fired, how much recoil would occur, would it cycle the slide?
    It depends, Bob. If the bullet travels deep enough into the barrel for the slide to move to the linkdown position, the squib will very often drive it far enough to chamber another round...also very often wothout the shooter knowing it. The second round bulges the barrel if it's carbon steel...and splits it if it's stainless. I've actually watched that happen...was looking straight at the gun when the squib ejected the case, and couldn't get the shooter's attention before she fired the "killing" round. Scratch one very expensive barrel installation. The slide didn't move on the second round. The bulge in the barrel locked it up tight.

    Without the bullet's continued forward drag on the barrel...it just doesn't take a lot of force to drive the slide.

    But...If the bullet is completely blocked by the stuck bullet...no. The slide won't move. It can't. If the bullet bears forward on the barrel while the equal/opposite force is pushing the slide...the forces are balanced and nothing can move. As you know...things move when forces become unbalanced. Balanced force is equilibrium.

    The added resistance of the small radiused firing pin stop is very small compared to the delaying force that the bullet places on it. It adds little to the total...but it adds it at just the right time, and as an engineer, you're well aware that sometimes a small thing can make a big difference...and that while nothing is everything, everything is something. Even the mass of a drop of water on the slide will have an effect.

    Another delaying factor that many don't consider is that of the barrel's mass. The barrel weighs about 3 ounces, and that's added to the total reciprocating mass...and it's part of until the barrel is completely disconnected from the slide. That's about 1/5th the slide's mass. That's signifigant.
    Last edited by 1911Tuner; 2nd February 2010 at 21:15.


  2. #22
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    Bob W - you don't have to apologize for anything - your thoughts are well presented and not the least bit offensive. Our Tuner has posted a convincing rejoinder - and anything that stimulates him to show us his Yoda qualities is always appreciated. It is through the exchange of ideas in this special cyber-space that we all learn and grow.

    If you haven't availed yourself of the opportunity, there is a 50+ page thread in this section of the forum in which John (The Tuner) and some bright engineers like you thrashed the daylights out of the subject. The sequel to that thread now written by Tuner is to help us mere mortals understand "how" and "why" it feels different to shoot a 1911 equipped with a small radius FPS vs. the larger radius designed by Colt long after JMB was out of the picture.

    It has been established to a final conclusion by anecdotal and visual evidence that the 1911 - once returned to the system configuration designed by JMB - has noticeably different and preferable recoil characteristics. That point is beyond argument. EGW'S sales volume of the part in question would probably be sufficient evidence by itself.

    I am neither an engineer nor very smart in the math and science world - but I think Tuner's final example involving a wall and pushing on the wall takes care of the subject. If you believe the gases are generating an opposing force after the bullet leaves the barrel, against what are the gases pushing to generate an equal but opposite reaction? I've shot 30-06 blanks and felt very little, if any, recoil. So, as Tuner explained, the primary application of force is the effect of the barrel resisting the movement of the bullet - which ends when the bullet is gone (I hope I got that right).

    Robert - really great pictures, and really clean work on the FPS - I am impressed! My work pales in comparison.

    George
    "Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life and who are willing to consciously work and sacrifice for that freedom." -- President John F. Kennedy

  3. #23
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    LJA...Quick physics course. Newton's laws of Motion and Conservation of Momentum is about all you need to understand it. Simplified form.

    1A. Objects at rest will remain at rest unless an outside force compels them to move.
    Newton was describing inertia.

    1B Objects in motion will remain in motion until an outside force compels them to stop.
    Conservation of Momentum.

    Skip 2. No real need since we're talkin' straight line motion.

    3 For every action, there must be an equal and opposite reaction.
    Here, Newton was telling us that force forward is force backward...that whatever force is applied in one direction must be applied in the opposite direction. If you push on it, you get pushed. If you pull on it, you get pulled.

    Force moves things. Momentum keeps them moving. Inertia resists a compelling force.
    Things only move if the forces...the compelling and the resistive forces...become unbalanced. That is, the compelling force is greater than the resistive force. If the forces are equal...balanced...there can be no motion. Balanced force means equilibrium. Applying 100 pounds of lifting force to a 100 pound weight doesn't move the weight. Applying 101 pounds does.

    The faster you try to accelerate a mass, the harder it fights. You can lift a 25 pound weight off the floor at a rate of 1 foot per minute pretty easily. Try to lift it at a rate of one foot per second, and it gets more difficult. The weight/mass hasn't changed, but the force requirement to accelerate it does.

    Weight and mass aren't the same. In outer space, a baseball and a 50-foot diameter boulder weigh the same. Nothing. You can move the baseball easily. Not so for the boulder.

    Newton 3 applies in all directions, with all vectored forces. Vectored meaning that it has magnitude and it has direction. If you pull a box across the floor, the box feels a frictional resistance, and the floor feels the same frictional resistance...in the opposite direction. Same goes if you push it. Hence, force forward is force backward. Always.

    Conservation of Momentum means just that. If you fire a bullet in space, away from atmospheric friction and the gravitational influence of another body, it will continue to travel at the exit speed forever...or until it strikes something or until it comes under the influence of gravity.

    Interestin' stuff, eh what?

    Bedtime. 0400 comes early around here.
    Last edited by 1911Tuner; 2nd February 2010 at 21:39.


  4. #24
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    Sweet dreams Tuner - and thanks. I really did flunk physics - wish I'd had you as my coach - I actually understand what you write. I appear to have successfully lived my life in strict accordance with Newton's Law 1A as worded by you!

    I appreciate the time you put into that post (and all the others). I got my law degree in 74 - and - thanks to the Great Spirit - it required no math or science. Now I am getting a ton of satisfaction from learning all kinds of new stuff in a subject that is near and dear to me - and you have been and continue to be a major part of that education. Mucho gratitude, hombre.
    "Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life and who are willing to consciously work and sacrifice for that freedom." -- President John F. Kennedy
    Last edited by LJA; 3rd February 2010 at 01:18.


  5. #25
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    My pleasure, George.

    In reference to Bob's question on whether a fired bullet into a barrel blocked by a squib...would recoil occur:

    Several years ago, a savvy old pistolsmith in Maryland decided to settle an argument over Kuhnhausen's "Balanced Thrust Vector" description of the 1911's function.

    He lathe-turned a steel rod, with one end form-tunred to exactly match the hardball nose profile. He threaded the muzzle of a worn barrel, and used a set screw to place the rod in solid contact with a chambered round, so that any possible bullet movement would be absolutely blocked.

    He then proceeded to fire the gun repeatedly to show that if the bullet doesn't move, neither will the slide. Nothing happened when the gun was fired. No kaboom and no slide movement. Nothing.

    What he didn't understand...and probably still doesn't...is that in his attempt to disprove JK's "Balanced Thrust/Force Vector" he actually created one. The bullet pushed on the rod, which was attached to the barrel via the set screw. As the force pushed the barrel forward and the slide rearward, which were locked by the lugs and thus prevented from separating. The force was equal on both barrel and slide. Neither one moved because neither one could move. They were locked in a state of equilibrium. Balanced force.

    He has stated often that the bullet provides the slide with momentum...but it doesn't.

    Force and the motion that results from the force provide the slide with momentum.
    Momentum is a function of mass times velocity. If it doesn't move, it doesn't have any momentum. It has inertia...resistance to compelling force.

    The bullet is moving in the wrong direction to provide the slide with anything. The forward moving bullet can't make the slide move any more than you can push a lawn mower by turning around and running from it. What the bullet provides is a resistance for the force to push off of...and the slide provides a resistance for the force to push off of in driving the bullet. If you're suspended in mid-air and frog-kick your legs, you can't propel yourself forward. If your feet are placed against a wall...you can.

    Action and reaction require two interacting objects and two forces. Remove one, and the system doesn't work. Or, another way...if the bullet is gone before the slide moves, it may as well have never been there, because one side of the equation is missing...the action side. Without action, there can be no reaction, and with balanced force, there can be no motion. If any part of the system is in motion, it's proof that the forces have become unbalanced at some point.

    His assertion that: "If the bullet doesn't move, the slide won't move" is technically correct...but not for the reasons that he thinks. When the bullet moves forward...it's slipping through the barrel. When the bullet can slip forward, the barrel can slip backward. So, it's more accurate to say that if the BARREL can't move, the slide can't move. In his demonstration, the slide was mechanically blocked by the barrel and the bullet.

    Incidentally, his demo also lends proof to my assertion that the bullet is the main delaying force in the design. In this, the bullet imposed the ultimate delay. It completely blocked rearward barrel movement...and the slide didn't move. Therefore, a frictional resistance placed on the barrel by the bullet would also be imposed on the slide for as long as the bullet is present.
    Last edited by 1911Tuner; 3rd February 2010 at 07:39.


  6. #26
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    That's very interesting!

    Out of curiocity, what happened when the gun was fired in this manner? Where did the expanding gases go??

  7. #27
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    Quote Originally Posted by rekladan
    Where did the expanding gases go??
    They leaked out the breech area with a PSSSSSSSSSS.

    Incidentally, after the demo, he removed the blocking mechanism, and fired the gun normally. It worked fine.

  8. #28
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    Quote Originally Posted by 1911Tuner
    Here's a very old X-ray...probably a fluroscope photo...of a 1911 pistol in motion about a millisecond before the bullet clears the muzzle...



    Is that the shooters hand in that ghostly image around the grip???? How would they have had the shutter speed to catch the bullet in flight??? I have always been told this image depicted a static X-Ray of a barrel obstruction.????
    Last edited by 10851Man; 3rd February 2010 at 10:45.


  9. #29
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    Quote Originally Posted by 10851Man
    I have always been told this image depicted a static X-Ray of a barrel obstruction.????
    No idea about the x-ray techniqes used, but note the position of the barrel's radial locking lugs in the slide lug recesses.

    While this could have been rigged, this position indacates the slide is in the process beginning to pull the barrel aftward.

    In a static (unfired) mode, the barrel lugs would be at the back of the slide lug recesses.

    Regards
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]

  10. #30
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    Quote Originally Posted by 10851Man
    Is that the shooters hand in that ghostly image around the grip????
    Yep...or rather the bones in the shooter's hand.


    Quote Originally Posted by 10851Man
    How would they have had the shutter speed to catch the bullet in flight???
    Dunno. It probably took several tries to catch it just right.


    Quote Originally Posted by 10851Man
    I have always been told this image depicted a static X-Ray of a barrel obstruction.????
    If there was an obstruction, it would show up as a solid, dark object...like the bullets in the remaining rounds in the magazine. The light-colored area behind the bullet is the gas plug that's pushing it. The "obstruction" theory was started by the people who buy into Kuhnhausen's "Balanced Thrust Vector" description in which the slide doesn't move until the bullet exits. Their minds are made up, you see...and they won't permit any factual evidence to interfere with that.

    Plus...if the bullet had in fact stuck a solid obstruction, the slide and barrel would have been yanked forward, and the link wouldn't be in the position shown.

    No. This pistol is firing...and this is a very old photo. Note that it's a pre A1 model.
    The photograph was probably done to settle an argument back then over whether or not the slide moves before the bullet exits. Newton says that it can't happen that way. That's all that's really needed to understand it.

    To wit:

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

    Equal being the operative word. Equal means equal...in every way. That includes setting the system in motion.

    Note also the engagement of the upper lugs. The front faces of the barrel lugs are in contract with the rear faces of the slide's lugs. The slide is being driven rearward, and it's dragging the barrel with it.

    The link is within a few thousandths of an inch of the start of the linkdown position.

    This is how the short recoil design functions.
    Last edited by 1911Tuner; 3rd February 2010 at 11:05.


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