Python end shake
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  1. #11
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    That makes perfect sense, and that's why I'm not too worried about it. The Python cylinder assemblies are seldom perfectly straight and true (which becomes evident when you measure the barrel gap on each chamber) so zero endshake is difficult to accomplish without inducing friction. There also machining marks you have to take into account, so if you fit a cylinder to zero endshake you will have two slightly rough surfaces rubbing against each other. It would be different if the surfaces were polished, perfectly true and parallel with each other, but they're not. A revolver is basically a machine, and if you build a machine without bearings you don't need to tighten up the tolerances too much.

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  2. #12
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    Thank you everyone for the info. I E-mailed Frank Glenn however he simply mentioned possible lead spitting at a BC gap of .008, this is not something I have noticed although I am not sure I would during normal shooting. He also mentioned measuring the BC gap with the maximum feeler gauge that will allow dry firing all six chambers. 2 of the chambers measured .009 BC gap with .003 endshake, 1 chamber was tighter with .008 BC gap and .002 end shake, and 2 measured at .010 with .004 end shake. So if I understand correctly does that put the BC gap and therefore the resulting end shake at the smaller measurement and therefore within spec? He also mention holding the cylinder back and measuring headspace. I am confused by his reply and the difference between BC gap and headspace. Either way my current plant is to continue to occasionally fire it using mostly .38s and maybe the occasional cylinder of light 357 and just keep an eye on the measurements to see if it gets worse.

  3. #13
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    Barrel-cylinder gap is just that.

    Head space is at the rear of the cylinder.
    That's the space between the frame breech face and the cartridge case head.

    All of this has to be taken into effect when building or inspecting a revolver. Head space only gets bigger when the cylinder develops cylinder end shake.
    Wear or battering allows the cylinder to move forward. When it moves forward the head space opens up.
    Correcting end shake also corrects head space unless the gun was defective from the factory or something is wrong.

    One reason for varying barrel-cylinder gap is if the cylinder crane is sprung, or bent. That causes the cylinder to "wobble" and the gap will open and close.
    Cranes usually get bent by someone flipping the cylinder open and shut with a flick of the wrist, sometimes known as "Bogarting" the gun, ala Humphrey Bogart.

    If you send the gun to Glenn he'll check all this out and correct it back to factory standards and specs..

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  5. #14
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    I guess I have one more question. All of these measurements were taken while the action was at rest, which is the method I saw described in a previous post. On a Python however, when the trigger is at the rear most position during firing, the cylinder will be at full "bank vault" lock up, with the second notch of the hand engaging the cylinder. Since there is no movement at the point of firing, how would the cylinder "hammer" the frame of the firearm, and why would the measurements at rest even matter? What am I missing?
    Last edited by GhostJim; 02-19-2018 at 06:57 PM.

  6. #15
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    The cylinder is tightly locked from ROTATION, but firing energy will push the cylinder both forward and back.
    This is Newton's Law in action; "For every action there's an equal but opposite reaction".

    First the cylinder moves forward as the firing pin strikes and the gun begins to recoil. The cylinder attempts to remain still while the frame moves to the rear. The frame impacts the cylinder at the front.
    Then the cylinder moves to the rear pushed by the bullet moving forward and the cylinder impacts the frame at the rear.
    Then the cylinder just bounces back and forth inside the frame until the energy is dissipated and the cylinder comes to rest.

    Measurements are taken with the action at rest because when cocked there is some spring pressure in the action that can cause false readings.
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  7. #16
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    If it were mine with those numbers I would retire it or send off for repair. Long run it will be economical to fix before more wear is seen.

  8. #17
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    Quote Originally Posted by dfariswheel View Post
    The cylinder is tightly locked from ROTATION, but firing energy will push the cylinder both forward and back.
    This is Newton's Law in action; "For every action there's an equal but opposite reaction".

    First the cylinder moves forward as the firing pin strikes and the gun begins to recoil. The cylinder attempts to remain still while the frame moves to the rear. The frame impacts the cylinder at the front.
    Then the cylinder moves to the rear pushed by the bullet moving forward and the cylinder impacts the frame at the rear.
    Then the cylinder just bounces back and forth inside the frame until the energy is dissipated and the cylinder comes to rest.

    Measurements are taken with the action at rest because when cocked there is some spring pressure in the action that can cause false readings.
    I can see how this would be the case with other revolvers, but I am still confused as to how this would happen in a properly timed Python because of Colt's unique action. When my Python is at full lockup, (with the trigger all the way to the rear), I cannot physically create any movement in the cylinder. Not with either forward or rearward pressure because of the lock up created by the hand. I am of course not exerting extreme pressures on the firearm, but the hand does not release the cylinder until the trigger is released and the action is returned to rest.Perhaps a better explanation than what I am giving - "In this action, the hand that rotates the cylinder pushes the cylinder into a tight lock-up and holds it there under pressure. The harder the trigger is pulled (within reason) the tighter the cylinder is locked in place."
    It's this lock up, under pressure, and at the time of ignition that should not allow any movement throughout the recoil process. All forces exerted on the cylinder would be absorbed by the hand which would be preventing any movement. In order to move the cylinder at full lockup the hand would have to physically move, which would cause trigger slap or damage the hand. It is this lock up that any Python owner should be able to reproduce by holding the trigger to the rear and exerting pressures on the cylinder. A properly timed Python should have no rotation or movement.

  9. #18
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    Upon further inspection I believe I am wrong about trigger slap. I can open the cylinder and push the hand back independently without any interaction on the pulled trigger. However with the gun at full lock up there is no movement in my cylinder whatsoever. I would also like to note that my theory on the lock up of the Python at the time of ignition seems to match with the method Frank Glenn described in his E-mail for measuring BC GAP. He stated that it needed to be the largest size feeler that would dry fire on all six chambers. Dry firing would mean full lock up, and I feel that unless there is something I am missing, this would mean that full lock up is the measurement that matters. Which again, on a properly timed Python, that should be zero movement and according to Frank Glenn a BC gap of .008 or less to prevent lead spitting.

  10. #19
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    Quote Originally Posted by dfariswheel View Post
    The cylinder is tightly locked from ROTATION, but firing energy will push the cylinder both forward and back.
    This is Newton's Law in action; "For every action there's an equal but opposite reaction".

    First the cylinder moves forward as the firing pin strikes and the gun begins to recoil. The cylinder attempts to remain still while the frame moves to the rear. The frame impacts the cylinder at the front.
    Then the cylinder moves to the rear pushed by the bullet moving forward and the cylinder impacts the frame at the rear.
    Then the cylinder just bounces back and forth inside the frame until the energy is dissipated and the cylinder comes to rest.

    Measurements are taken with the action at rest because when cocked there is some spring pressure in the action that can cause false readings.
    I have tried to wrap my head around this in the past, and I believe it could actually start with the cylinder moving to the rear. The cartridge expands when the cartridge is ignited, and this would make it stick to the chamber and pull the cylinder to the rear before the bullet exits. Once the pressure drops, the cartridge comes loose again and is free to bounce back and forth with the rest of the parts.

    Not that it matters much, it's just one of those things that keep me up at night.

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  11. #20
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    There's a difference between manually trying to move the cylinder back and forth, and firing a live cartridge.
    The cartridge pressure will move things around, and while not being into physics, I'd imagine the frame itself flexes slightly, making room for the cylinder to move.

    As for which way the cylinder moves.........
    The first force that acts on the cylinder is the impact of the firing pin on the cartridge, which drives the cylinder forward.
    When the cartridge fires the force would push the cylinder to the rear, but I think that what actually happens is the rearward thrust of the cartridge against the frame causes the frame to move rearward while Newton causes the cylinder to attempt to remain stationary.
    After that everything is bouncing around like a rubber ball.


 
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