Welcome to M1911.ORG
The M1911 Pistols Organization Forums Site


John needs your help
Please read this message.


Sponsors Panel
If you intend to buy something from the companies advertising above, or near the bottom of our pages, please use their banners in our sites. Whatever you buy from them, using those banners, gives us a small commission, which helps us keep these sites alive. You still pay the normal price, our commission comes from their profit, so you have nothing to lose, while we have something to gain. Your help is appreciated.
If you want to become a sponsor and see your banner in the above panel, click here to contact us.

Page 1 of 10 12345 ... LastLast
Results 1 to 10 of 100

Thread: Explanation of the operation of EGW Firing Pin Stop

THREAD CLOSED
This is an old thread. You can't post a reply in it. It is left here for historical reasons.Why don't you create a new thread instead?
  1. #1
    Join Date
    1st June 2004
    Location
    Lexington, North Carolina...or
    Posts
    11,260
    Posts liked by others
    29

    Explanation of the operation of EGW Firing Pin Stop

    I've been able to clear a little off my plate today, so I'll go ahead with the explanation of all the factors at work whenever the radius of a simple firing pin stop is changed...and how they affect the recoil cycle of the 1911 pistol.

    In the interest of a smoother flow, I ask that comments and questions be held until I've finsihed. I need to split this up into two or three separate segments to keep it from dragging on for too long. I've found that people who are reading an overly long text tend to skim over a lot of it...or skip it outright...the instant that they find something that they don't understand or disagree with. I won't argue these points. I've already done that too much, and I don't have to time. Instead, I'll describe the function and the physics involved, and let everytone decide for themselves whether they want to accept it or not.

    First...a few things that we need to clarify and accept as simple physical and mechanical fact.

    Force forward=force backward. Always. If X units of force is applied, it applies in all directions. Thus...if X units of force is brought to bear on a closed system, it's applied backward and forward in equal measure. This is known as a "vectored" force. That is...it has magnitude and direction.

    Recoil is nothing more than backward acceleration in response to a force applied to a closed system in which at least one side of the system is moveable. Even if the recoil impulse doesn't produce movement, it still occurs. The reason that no movement is seen on the reaction side is because the force wasn't large enough to overcome the level of resistance offered by the reaction side. A 500-pound .223 caliber rifle may be used as a demonstration. Actgion and reaction occur, but you can't detect reaction due to the mass and the force applied to that mass.

    Recoil only occurs when acceleration is applied. Once the acelerative force is removed, there is no further acceleration...and hence, no more recoil. What we perceive as recoil is mostly momentum that was conserved while the accelerating force was on the system. The actual recoil impulse is over so quickly that we scarcely have time to detect it.

    When the bullet exits, the force is removed from the system, and neither bullet nor breechblock can accelerate further. All movement after the force has been removed is due to conserved momentum. For both sides, all they can do is decelerate due to outside forces that they encounter.

    Any outside force that is imposed on the system while under an accelerating force will affect the rate of acceleration, and the remaining momentum that is conserved during the acceleration. Anything that has the opportunity to to affect the object's motion will do just that. Once momentum is lost, it can never be regained unless a "new" force is applied.

    Force makes things move. Momentum keeps them moving. Force robs moving objects of speed and momentum.

    Recoil operated pistols and straight blowback pistols are both recoil operated. Blowback is misleading. The only real difference is in the mechanical method of delaying the breech opening until the bullet has exited, and pressure drops to a safe level.

    In the short recoil system, the bullet is the main delaying factor. Go back to force forward=force backward. The barrel imposes a frictional resistance to the bullet. Whatever friction the barrel offers to the bullet, the bullet offers to the barrel. The barrel moves backward while the bullet is moving forward...each one resisting the other. All other delaying forces...recoil spring...mainspring...slide mass...barrel mass...and slide to frame friction are secondary to the bullet's influence.

    Small changes to the outside forces resisting the slide cause large changes to the slide's rearward travel, and the earlier in the slide's acceleration the decelerating force is applied, the larger its effect on the slide's rate of acceleration and its conserved momentum.

    In an autopistol...regardless of the design...we feel very little recoil, if any, as a result of the internal ballistic event...or the "explosion" of the powder. The gun is comprised of the barrel and the breechblock...the slide. The frame is essentially a gun mount with no solid connection to the gun. None of the actual recoil impulse is transmitted directly to the frame that way it is in a fixed-breech revolver or bolt-action rifle.

  2. #2
    Join Date
    1st June 2004
    Location
    Lexington, North Carolina...or
    Posts
    11,260
    Posts liked by others
    29
    Next, we'll recap the basic function of the short recoil system...just to keep it fresh.

    When the pistol fires, the action/reaction begins immediately. The slide starts to move as soon as any headspace is filled by the backward-moving case when it begins bearing on the breechface. Because quick pistol powders peak rapidly, full pressure and force is brought to bear on bullet and breechface within a half-inch of bullet travel...or less...depending on the power's burn rate.

    At approximately .100 inch of slide travel, the bullet exits, and the slide continues rearward on its conserved momentum. During the time that the bullet is still present and being forced through the barrel and the slide is likewise being driven in the opposite direction, its forward drag on the barrel is working to delay the slide. Remember that the slide is the recoiling part of the system...not the barrel. The barrel is forced to move backward with the slide because the locking lugs are horizontally engaged in opposition. This is the "locked" function of the locked breech.

    This phase only lasts for a short time and distance...hence the name "Short Recoil" operated. Again...once the bullet clears the muzzle, all accelerative force on the system exits behind it, and the actual recoil event is over. There must be two interaction objects in an action/reaction event. When one is removed from the system, action and reaction can't exist, and any further movement of either object is due to momentum.

    Momentum is a function of mass X velocity. In order to reduce the momentum, the velocity must be reduced. This reduction comes from outside forces that oppose the object's movement. Anything that can oppose the movement will oppose it.
    Once momentum is lost, it can't be regained unless a new force is brought to bear on the object.

    No force...No acceleration.

    If momentum reduction is the goal, the best time to invoke a resistive force is at the beginning of the acceleration...before it gains a full head of steam. Once full momentum is aquired, any outside force must work harder to reduce velocity and momentum. In the short recoil system...The earliest application of outside force is applied by the bullet itself. Next in line is the hammer and mainspring. Last...and least effective...is the recoil, or action spring.

    The so-called recoil spring's primary function is in returning the gun to battery. Decelerating the slide is a natural consequence of its compression by the slide's travel...but that's incidental. The two main outside forces working to slow and delay the slide are the bullet and the hammer/mainspring assembly...because they are brought to bear early in the event.

    Stay tuned. The final installment is in the offing.

  3. #3
    Join Date
    1st June 2004
    Location
    Lexington, North Carolina...or
    Posts
    11,260
    Posts liked by others
    29
    After a few years and dozens of pages of discussion on the reduced radius firing pin stop, we've come to understand that it delays the slide for a split fraction of a second by way of reducing the slide's mechanical advantage in compressing the mainspring... and that by doing so at the beginning of the slide's acceleration...it produces a telling effect on the slide's rearward velocity and momentum. Many people report a more user-friendly gun...either in reduced muzzle flip...smoother operation...faster split times, or whatever each shooter experiences. Sometimes, it's not really any one thing, or anything that we can put our finger on.

    First, lets look at the recoil system...the separate closed system that actually produces the felt recoil in an autopistol.

    Virgil Tripp's excellent slow motion and stop-action videos clearly show that the pistol moves very little until the slide hits the impact abutment in the frame...and that the bulk of muzzle flip occurs there...but the pistol does move a little as the recoil spring compresses. Force forward=force backward. Whatever force the recoil spring produces is returned to the gun, onto the slide and frame.

    The reduction in slide velocity means that the spring is compressed more slowly, which spreads out the rearwaed push on the frame over a longer time...but there's another aspect of that increased time frame. Because the slide also has reduced momentum, the spring decelerates it at a faster rate...which contines to decelerate the slide, until it hits the frame. Thus, the whole would appear to be greater than the sum of its parts.

    But there's another "hidden" aspect to consider...something that has a greater effect on the cycle than the immediately apparent of reduced mechanical advantage. Timing. I'm not talking about the mechanically fixed timing of the barrel. The variable timing of the bullet's exit relative to the slide's position.

    We know that the bullet exits at (nominally) 1/10th inch of slide travel...but that's not chisled in stone. It can vary a little from gun to gun.

    At no point in the event is the pressure..and the force that it produces...higher than at the instant of peak pressure. Pistol powders peak rapidly, and fall off rapidly. It's entirely possible for the bullet to be moving at a higher speed at some point in the barrel before exit than it's moving at the muzzle.

    BUT...as long as the bullet is IN the barrel, and is being pushed by unbalanced force...the same force is driving the slide...helping it get past that little speed bump that the hammer and mainspring impose in conjunction with the FP stop radius.

    The "hidden" effect of the radius is that it delays the slide at the instant that it's trying to overcome that speed bump...and the bullet is still headed for the muzzle.
    There is no added speed bump...no "extra" force to impede its progress other than the friction imposed by the barrel, and that's a constant...assuming all eles is equal. The result is that the bullet exits earlier relative to the slide's position. It still requires the same amount of time to traverse the barrel...but as far as the slide knows...it got loose earlier, and thus removed the accelerating force that was helping the slide get past the speed bump...which multiplies the effect of that speed bump, and robbing the slide of momentum. So...rather than the bullet exiting at 1/10th inch of slide travel...it escapes at .090 or maybe even less slide travel. .010 inch doesn't sound like a lot...but it amounts to 10% of the short recoil function. 10% reduction in slide velocity and momentum and striking energy at the frame IS signifigant. It equates to reducing the bullet's muzzle velocity by 10%...or more than the difference between firing equal rounds in a 5-inch gun and a Commander..except there no reduction in bullet speed. The reduction is all rearward.

    Simplified: The stop helps to delay the slide which allows the bullet to escape earlier in the slide's cycle which removes the force from the slide earlier which leaves the slide with no force to accelerate it which gives the spring MORE time to decelerate it before it strikes the impact abutment.

    The early release of pressure and force is a factor that many consider...even the people who understand the initial effect reduced radius. It's easy to grasp that. hand-cycling offers proof because it's slow enough for us to feel it, and because we're the ones providing the rearward force on the slide. When it speeds up to ballisitic level, and the cartridge is providing the force instead of hand and arm strength...it's a little harder to catch.

    Think of it like this:

    If you stand with your hands against a wall and shove...you accelerate away from the wall, and you continue to accelerate as long as your hands are in contact with the wall, and you continue to apply force. Once you've pushed yourself far away enough for your hands to lose contact...there is no more force...and no more acceleration. You continue to move backward on momentum.

    If you stop applying force before your arms are straight...you still lose contact with the wall, but you lose it earlier...and your momentum doesn't carry you as far from the wall.




    Note from John: I'll leave this thread run its course here, and then we'll make it a sticky and move it to the Sticky Gunsmithing Threads forum, so that it can act as a reference.


  4. #4
    Join Date
    23rd January 2007
    Location
    Texas
    Posts
    328
    Posts liked by others
    0
    An incredible and easy to understand explanation, Tuner. Please turn your three posts into a sticky and delete mine. A million thanks! It might be best to start a thread to separately discuss your short anthology of "how" and "why" the small radius FPS makes such a difference. JMB is patting you on the back, old son. 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

  5. #5
    Join Date
    16th January 2005
    Location
    Uniontown,Oh.
    Posts
    664
    Posts liked by others
    5
    THE BEST explanation I've ever seen. Ever since changing to an EGW,I've felt the difference. Another way to feel the interaction is to cock the hammer and then see how easy the slide moves rearward when cycling it by hand.EXCELLANT.
    "Carry the battle to them.Don't let them bring it to you.Put them on the defensive and don't ever apologize for anything"-Harry S. Truman

  6. #6
    Join Date
    18th May 2009
    Location
    Fresno, CA.
    Posts
    732
    Posts liked by others
    1
    Quote Originally Posted by 1911Tuner
    "The stop helps to delay the slide which allows the bullet to escape earlier in the slide's cycle which removes the force from the slide earlier which leaves the slide with no force to accelerate it which gives the spring MORE time to decelerate it before it strikes the impact abutment...."
    Tuner,

    I have the EGW FPS on all my guns. The first one went into my 1927 Colt-Hartford Argentine and I immediately noticed the gun had a sharper initial recoil impulse, but less flip and dip of the muzzle. This was most noticeable during rapid fire strings.

    I have also noticed something else about the EGW FPS; a cleaner chamber/ejection port area.

    I have a Nornico 1911-A1 which is my demo/range gun that I use for training. It originally had the 5/64" radius FPS, 23lb mainpsinrg and 16.0lb recoil spring. In this conforguartion, the breech would get filthy, whereas the breech on my 1927 Colt-Hartford stayed very, very clean, even shooting the same ammo.

    When I swapped the EGW FPS into my Norinco, the breech stayed very clean, but I saw more soot on the muzzle, barrel bushing, recoil spring plug and sides/top of the slide.

    This, I think, is evidence of the reduction in chamber pressures when the gun unlocks with the EGW FPS.

    Additionally, I used to agonize over getting the right radius on the EGW FPS. After several thousand rounds through my 1927 Colt-Hartford Argentine, I noticed the hammer made its own radius.

    Now, I simply break the edge on my stone and let the hammer do the rest...Robert
    Last edited by 10851Man; 1st February 2010 at 10:31.


  7. #7
    Join Date
    13th December 2009
    Posts
    26
    Posts liked by others
    0
    Quote Originally Posted by 10851Man
    Tuner,

    When I swapped the EGW FPS into my Norinco, the breech stayed very clean, but I saw more soot on the muzzle, barrel bushing, recoil spring plug and sides/top of the slide.

    This, I think, is evidence of the reduction in chamber pressures when the gun unlocks with the EGW FPS.
    I noticed the same thing on my RIA Tactical, now I have an explanation as to why this happens. Thanks.
    Last edited by Johnnykck; 1st February 2010 at 11:56.


  8. #8
    Join Date
    21st September 2008
    Posts
    9,964
    Posts liked by others
    209
    Here's one of the Tripp Research videos that Tuner refers to. After watching it, watch it again and this time keep your eyes on the shooter's hand, and how it reacts to the slide hitting the frame at the end of its rearward travel.

    http://www.youtube.com/watch?v=AMdr5HQWUck

  9. #9
    Join Date
    23rd January 2007
    Location
    Texas
    Posts
    328
    Posts liked by others
    0
    I would love to see the same video sequence after a small radius FPS has been installed. Thanks for posting the link. 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

  10. #10
    Join Date
    1st June 2004
    Location
    Lexington, North Carolina...or
    Posts
    11,260
    Posts liked by others
    29
    The stock NOrinco FP stop radius is 7/32nds which became the standard on January 1st, 1918. Browning's original was 5/64ths. Chamber pressure must be at or near atmospheric when the breech opens. That's the whole point of delay.

    The sharper inpulse is due to a more "solid" connection between slide and frame. The initial impulse is transferred faster, but channeled in a different direction. The push from the recoil spring is slower and the slide to frame impact is less intense...which results in less muzzle flip...which is why the gun gets back on target quicker.

Page 1 of 10 12345 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  



Sponsors Panel
If you intend to buy something from Brownells, please use their banners above. Whatever you buy from them, gives us a small commission, which helps us keep these sites alive. You still pay the normal price, our commission comes from their profit, so you have nothing to lose, while we have something to gain. Your help is appreciated.
If you want to become a sponsor and see your banner in the above panel, click here to contact us.

Non-gun-related supporters.
Thank you for visiting our supporters.