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  1. #1
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    Default Free floating firing pins

    After learning that most semi auto rifles don't have spring loaded firing pins - I started wondering - why is that the case and how do they work reliably without constantly slam firing? Also if a firing pin isn't being kept in position by a spring, what ensures that it comes to rest in the right place after firing?

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  2. #2
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    Default Re: Free floating firing pins

    The firing pin is light enough to not cause a slam-fire when chambered. Most (I know my Type 56 does) will however leave a small indent on the unfired primer when chambered. This dent is not deep enough so that it fires the primer. Also keep in mind that rifle primers are much harder than pistol primers, specifically with this in mind. It MIGHT slamfire when using pistol primers (which is soft and has a thin cup).

    The firing pin is longer than the firing pin channel. This means that if the hammer comes to rest on the back of the firing pin, the front of the pin is pushed forward into the primer. Therefore if does not matter what position the firing pin is before being fired as it will always be slammed into the primer when the hammer hits it. The easiest way to explain this is to look at the Tokarev pistol or Norinco 213( same design but chambered for 9mmP instead of 762x25)

    Take a look at the picture below. It is a photo of a Tokarev with the hammer in it's fired position. You will notice that the face of the hammer touches the slide.



    Now take a look at when the hammer is lowered onto an unfired cartridge. You will notice that the hammer is now resting on the firing pin, which in turn pushes against the primer of the unfired cartridge.

  3. #3
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    Default Re: Free floating firing pins

    Quote Originally Posted by mic View Post
    The firing pin is light enough to not cause a slam-fire when chambered. Most (I know my Type 56 does) will however leave a small indent on the unfired primer when chambered. This dent is not deep enough so that it fires the primer. Also keep in mind that rifle primers are much harder than pistol primers, specifically with this in mind. It MIGHT slamfire when using pistol primers (which is soft and has a thin cup).

    The firing pin is longer than the firing pin channel. This means that if the hammer comes to rest on the back of the firing pin, the front of the pin is pushed forward into the primer. Therefore if does not matter what position the firing pin is before being fired as it will always be slammed into the primer when the hammer hits it. The easiest way to explain this is to look at the Tokarev pistol or Norinco 213( same design but chambered for 9mmP instead of 762x25)

    Take a look at the picture below. It is a photo of a Tokarev with the hammer in it's fired position. You will notice that the face of the hammer touches the slide.



    Now take a look at when the hammer is lowered onto an unfired cartridge. You will notice that the hammer is now resting on the firing pin, which in turn pushes against the primer of the unfired cartridge.
    Thanks mic! This clarifies it for me. Were free floated firing pins therefore chosen in some rifle designs to reduce complexity and cost in terms of design and manufacturing?

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  4. #4

    Default Re: Free floating firing pins

    Military ammo uses a harder primer. In the US you can get specific primers meant for military style rifles. Some, not all commercial primers are softer and can and do slam fire in military rifles.

  5. #5
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    Default Re: Free floating firing pins

    Free floating firing pins seem to be more reliable than other types. I know the South African R4 / R5 were retrofitted with springs and a polymer tube which contained the firing pin. Sometimes gunk would enter the tube and block the pin from freely moving forward / back. This resulted in the firing pin "sticking" and would unintentially cause a multi- round burst to fire with a single depression on the trigger, even when set to semi-auto.

    A simple fix for this problem was to replace the polymer tube which housed the pin.

    A free floating firing pin will not have this problem, but might cause an unintended discharge when charging the weapon.

  6. #6
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    Default Re: Free floating firing pins

    Quote Originally Posted by mic View Post
    Free floating firing pins seem to be more reliable than other types. I know the South African R4 / R5 were retrofitted with springs and a polymer tube which contained the firing pin. Sometimes gunk would enter the tube and block the pin from freely moving forward / back. This resulted in the firing pin "sticking" and would unintentially cause a multi- round burst to fire with a single depression on the trigger, even when set to semi-auto.

    A simple fix for this problem was to replace the polymer tube which housed the pin.

    A free floating firing pin will not have this problem, but might cause an unintended discharge when charging the weapon.
    Interesting. Thanks again. I've definitely learned something today.

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