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Ar-15 firing pin safety.

Discussion in 'Rifle Country' started by againstthagrane, May 21, 2010.

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  1. againstthagrane

    againstthagrane Member

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    Does it have one?

    If I drop a chambered ar-15 barrel first could it theoretically forcethe floating firing pin forward fast enough to ignite the primer?
     
  2. Mags

    Mags Member

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    No it does not have a firing pin block or safety, and that is why they train us not to chamber a round until you are ready to fire or in combat. But I really don't think it will fire from dropping the rifle on the barrel think about how fast the bolt flies into battery when you chamber a round, does the rifle fire then? Chamber a round and then eject it and examine the primer you will see what I am talking about. Most 5.56 ammo has a harder primer cup so it will not ignite during chambering. When you reload alot of manuals reccomend against the softer primer cups which I believe are made by Remington for this very reason, it would cause your gun to fire out of battery and eratically.
     
  3. taliv

    taliv Moderator

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    it floats freely. just chamber a round and remove it and you'll see the firing pin actually dented the primer (w/o setting it off)
     
  4. Steve in PA

    Steve in PA Member

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    SKS, Garand, M1 Carbine and some other rifles all have free floating firing pins.
     
  5. Rokman

    Rokman Member

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    Actually, I prefer Remington 7 1/2 primers for my AR loads or CCI, because they appear to have harder cups. Or maybe because that's what I have available. I have let the bolt slam countless times and have never had a slamfire. I always point it in a safe direction just to be on the safe side.
     
  6. Mags

    Mags Member

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    I looked it up and Remington SR 6 1/2s are what you are not supposed to use due to the soft cup, I just use CCI white box myself.
     
  7. Still 2 Many Choices!?

    Still 2 Many Choices!? Member

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    In a word no....

    The firing pin does not have enough weight to ignite a properly seated primer on it's own. The floating firing pin won't make a difference. If speed/mass of the bolt carrier closing the bolt won't do it, neither will a drop. It takes the force of the spring driven hammer to push the very light pin hard enough.
     
  8. Tirod

    Tirod Member

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    Remington doesn't recommend the practice of using soft primers, but it's more because the public doesn't like seeing the dimples and won't tolerate them. Military primers get dimpled too, it's not remarked because the weapon cannot fire out of battery.

    The length of the firing pin was calculated to be exactly right only when the bolt is closed and fully locked. The firing pin cannot protrude until the bolt head rotates enough, and it shortens the overall BCG length to do so. The locking lugs must be turning into engagement before the firing pin can stick out far enough to strike the primer. Even then it takes sufficient force from the hammer, a free falling pin would have to stop with such force the barrel would be seriously damaged by the impact.

    It's not impossible, it's nothing like a Colt SAA. Pull the bolt out and try it, you'll see how it works.
     
  9. Slamfire

    Slamfire Member

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    Unlikely on a chambered AR-15. Would depend on the distance of the drop. I don’t know the velocity an AR-15 firing has to reach to have enough energy to ignite the primer. The acceleration of gravity is 32 ft per second, maybe after a 16 foot to 32 foot drop right on the muzzle. Those velocities probably exceed the forward velocity of the AR15 bolt.

    Wrong.

    Slamfires happened to the early M16’s because of a heavy firing pin and sensitive primers. If you look in Chapter eight, page 130, of the “Black Rifle” by R. Blake Stevens, there is an entire section on the slamfire problems the Army had with the M16. A number of AR15 slamfire incidents had occurred when cartridges were single loaded and the bolt release pressed.

    If you read the report in the book, dated 1963, based on the tests of two rifles with the firing pin configuration available at the time, the energy during bolt closure of one of the test rifles firing pin always was above the “none fire” specifications of the primer. Which meant that statistically some of the primers would ignite at those energy levels. So the Army did two things. The first was to test alternate firing pin configurations, all pictured in the book, and one has a spring undoubtedly like the current AR-10 design, and the second was to change the ammunition specifications to require a harder primer.

    You can see the different firing pin configurations under Fulton Armory FAQ, the article “Slamfire: the M16 story” http://www.fulton-
    armory.com/


    I have been collecting posted incidents of AR15 slamfires
     
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