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Thread: Square cut firing pin stop - Downside?

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  1. #1
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    Square cut firing pin stop - Downside?

    So I was reading a few years ago that replacing the firing pin stop could reduce felt recoil in a 1911 pistol. The source I was reading didn't provide any other information than the only change that was made was a different firing pin stop, and they gushed about how much less the felt recoil was. I remember reading this and thinking to myself "Well that don't make ANY sense."

    Recently I was reading a post on a different forum, and the poster said that a square cut firing pin stop will reduce felt recoil compared to a beveled firing pin stop because it removes the mechanical advantage that the beveled firing pin stop offers to the rearward moving slide to overcome the mainspring and cock the hammer back. After reading THAT I thought to myself "OMG, that makes perfect sense. Why didn't I see that before?"

    And now I've given it some further consideration. We live in a world where physics works, and many of the laws of physics can be summed up together as "Nothing's for nothing." Felt recoil might be reduced, but all the energy is still right there, it's just moved around a bit.

    I'm thinking a square cut firing pin stop would probably redirect some of that recoil energy to the firing pin stop and the face of the hammer. Maybe the hammer pin, and the frame around the hammer pin hole.

    Does replacing a beveled firing pin stop with a square cut firing pin stop create any additional wear & tear on the pistol other than the firing pin stop and the hammer? Does the frame around the hammer pin hole need to be checked for wear & cracking more frequently? Does it help alleviate wear & cracking on other parts of the frame or the internals?




    For what it's worth, this was all in the context of a 6" 10mm 1911 being fed a steady diet of full Norma & hotter 10mm loads. Shooters were scrambling for heavier & heavier recoil springs to reduce felt recoil, all to no avail. One clever chap advised them to replace their beveled firing pin stop with a square cut one, and replace the main spring with the heaviest mainspring they could find. Shooters came back reporting near-miraculous results in felt recoil reduction. Being the cynical squig that I am I couldn't help thinking "But what's breaking now?"
    The people should not fear their government. Government should fear the people.

  2. #2
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    A long time ago 1911Tuner posted an explanation of this. You have the right idea, but some details are incorrect.

    First off, the current production firing pin stops are not "beveled," they are radiused. The radius is 7/32 of an inch. This was one of the changes made when the pistol was updated from the original M1911 to the M1911A1. The original M1911 firing pin stop was also radiused, but the radius was much smaller. IIRC, I think 1911Tuner wrote that it was 5/64 of an inch. It's not "square cut." EGW sells one that has a square cut, but it's not intended to be installed that way. EGW primarily supplies parts to gunsmiths. The intent is that the gunsmith will modify the corner to whatever radius he wants.

    https://forum.m1911.org/showthread.p...us+firing+stop

    https://forum.m1911.org/showthread.p...us+firing+stop

    1911Tuner also provides in those threads an excellent explanation of why the small-radius firing pin stop reduces felt recoil.
    Hawkmoon
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  3. #3
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    Thanks for the prompt reply Hawkmoon.

    In none of those quoted threads did Tuner or anyone else mention any possible excessive wear & tear on internals or the frame that might be caused by changing to a smaller radius firing pin stop. Can I assume that I'm making a mountain out of a mole hill, and that, once again, John Browning knew what he was doing when he made us this absolute DUMP TRUCK of a tough, rugged pistol?
    The people should not fear their government. Government should fear the people.

  4. #4
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    The short radius firing pin stop will add some load to the hammer and hammer pin. It will take load off of the barrel link lug and the slide. I think your overloaded 10mm will need all the help it can get, maybe even one of those trick multi-spring recoil assemblies.

  5. #5
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    Hammer needs same energy to get cocked. Recoil will not change unless you replace main spring with stronger one. In this case you will have decreased recoil but firing pin will be smashed harder, when you shoot.
    How about just replacing recoil spring with stronger one? Would it be too simple solution?

  6. #6
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    Quote Originally Posted by car5car View Post
    Hammer needs same energy to get cocked. Recoil will not change unless you replace main spring with stronger one. In this case you will have decreased recoil but firing pin will be smashed harder, when you shoot.
    Incorrect. The recoil energy of the slide will be the same (assuming always using the same ammunition, of course) but, because the point at which recoil energy is applied to the hammer is moved closer to the fulcrum, more of that energy has to be expended in cocking the hammer, leaving less energy to be absorbed when the slide hits the point of full retraction and stops.

    How about just replacing recoil spring with stronger one? Would it be too simple solution?
    Yes, that's an overly-simplistic solution, and can create other problems.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside
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  7. #7
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    Down side is I feel it puts more load on the Sear and Hammer pins.
    Not a big thing, but when i put on of those firing pin stops on a gun, I make sure the pins are good quality
    Colt brand are good, EGW makes theirs from drill rod, there are acouple of others too.

    Recoil spring can drop to 16 lbs, some say even 14 lbs.
    Mainspring needs to be 23 lbs.

    It's kinda a system, firing pin stop, hammer and sear pin, recoil spring, and mainspring

  8. #8
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    Quote Originally Posted by T-TAC View Post
    Down side is I feel it puts more load on the Sear and Hammer pins.
    Not a big thing, but when i put on of those firing pin stops on a gun, I make sure the pins are good quality
    Colt brand are good, EGW makes theirs from drill rod, there are acouple of others too.

    Recoil spring can drop to 16 lbs, some say even 14 lbs.
    Mainspring needs to be 23 lbs.

    It's kinda a system, firing pin stop, hammer and sear pin, recoil spring, and mainspring
    It does put more load on the hammer pin. I don't understand how it could possibly affect the load on the sear pin. In terms of the hammer pin, I would be more concerned with the holes wearing to an oblong than I would worry about the hammer pin breaking. For this reason, I don't think I would consider this modification on an alloy-framed pistol, only on steel frames.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside
    Last edited by Hawkmoon; 8th September 2020 at 10:32. Reason: typo


  9. #9
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    Interesting discussion. It makes sense to me that there would be more wear on the hammer pin hole from a small-radius FPS, compared to a large one... but with a steel frame of modern manufacture, I'd guess that the extra wear would be negligible enough to be academic. I'd wager that you'd wear the rifling off of many 10mm barrels, before you saw a noticeable effect on frame pin holes.
    Too many people miss the silver lining because they're expecting gold.
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  10. #10
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    For the average Gov't Model in battery, the hammer after firing makes initial contact with the FPS at a point above the FP hole as shown below on the right:

    P(09)8060002b EGW Pin Stop Modification, Post 177.jpg

    When a square bottom FPS is fitted for maximum reduction in perceived recoil (lower aft corner left square), the hammers contact point with the FPS is shifted about half way down to the center of the center of the hammer pin as shown in the center (or on the right by the broken line). I'm guessing this would decrease the slides mechanical advantage over the mainspring by a factor of 2 and increase the load on the hammer pin and its holes by a factor of 2.

    This, of course, relates to only the initial aftward movement of the slide after firing. After that....uh...things change
    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]
    Last edited by niemi24s; 8th September 2020 at 14:56.


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