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Thread: firing pin protrusion

  1. #1
    klayton83
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    firing pin protrusion

    this may be a topic all of you have already discussed but i was wondering what the perfect amount of firing pin protrusion is. i am using br4 primers if that makes a difference. the other day i had one that would not go off and so i lofted the bolt and inspected replaced and fired it again, and it went off. i would like to know that my rifle will never do this again. so i would like to adjust the firing pin and i took the bolt apart and can see that it can be adjusted. i just don't know what safe maximum protrusion would be without rupturing primers? ...

  2. #2
    Paid Member 82boy's Avatar
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    Re: firing pin protrusion

    Welcome to the site.
    Maximum protrusion, is not a good thing, as this actualy cuts down on the total amount of actual firing pin travel. Want you want is enough firing pin protrusion, to have a constant ingnigtion. Paul Mauser beliefe was that you need .050 protrusion, and that is what most people accept as standard. Sharp Shooter has ran the numbers, done expermints, and with the modern componets use today and the savage design, there is no need for that much travel, and his thought is it should be much less.
    Patrick
    "To win in bench rest, you dont have to shoot small groups, you just can't shoot any big ones." ;)

  3. #3

    Re: firing pin protrusion

    Not enough over travel in the trigger will cause missfires.

  4. #4
    Paid Member 82boy's Avatar
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    Re: firing pin protrusion

    Quote Originally Posted by nwkman
    Not enough over travel in the trigger will cause missfires.
    huh?
    Patrick
    "To win in bench rest, you dont have to shoot small groups, you just can't shoot any big ones." ;)

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    Re: firing pin protrusion

    Quote Originally Posted by klayton83
    the other day i had one that would not go off and so i lofted the bolt and inspected replaced and fired it again, and it went off.
    First did it show the firing pin strike? If it did the primer might not have been seated all the way down. If it didn't you might have had a false firing, i mean you triped the accu-trigger safety and need to unlock the bolt to reset the trigger.
    "And you shall know the truth, and the truth shall make you free. John 8:32 (New King James Version)

  6. #6
    klayton83
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    Re: firing pin protrusion

    i do not have an accutriger its actually a stevens 200 (i know there is another section for that but....). it did show a strike on the primer. i adjusted it a little the other night and loaded a dummy round with a live primer and it put a deeper mark in it. i tested it like 3 times and they all went off. like i said this only happened once it is just that i don't want it to ever happen when i need it to go off. this is chambered in 6br and i am using lapua brass. i just don't want it to start causing primer puncture. i read that the accuracy internationals sometime puncture some of the softer primers because the weapon was intended for combat use. I don't want punctures but i definitely want that maximum reliability. also this was first run on this brass and i have never had it happen with previously fired brass. i am thinking the combat protrusion minus about .1 or .05 maybe perfect...... thoughts?

  7. #7
    klayton83
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    Re: firing pin protrusion

    i ment minus .01 or .005

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    Re: firing pin protrusion

    Over travel, which is set to close can cause accuracy problems. Some over travel may be needed, to prevent sear from dragging on top of trigger. Also bolt removal may be difficult. A little extra trigger travel is better than not enough. When adjusting firing pin, check cocking piece pin in fired position. There should be about 0.005" clearance between pin & bolt body. If set without clearance it will limit firing pin travel.

  9. #9
    Paid Member Blue Avenger's Avatar
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    Re: firing pin protrusion

    Quote Originally Posted by 82boy
    Quote Originally Posted by nwkman
    Not enough over travel in the trigger will cause missfires.
    huh?
    I think he is referring to the sear dragging on the trigger if things get to tight.
    .223 Rem AI, .22-250 AI, .220 Swift AI .243 Win AI, .6mm Rem AI, .257 Rob AI, .25-06 AI, 6.5x300wsm .30-06 AI, .270 STW, 7mm STW, .416 Taylor

  10. #10
    klayton83
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    Re: firing pin protrusion

    i don't think that there is any problem with the trigger mechanism. I did notice that there needs to be a little more clearance between the cocking pin and the bottom of the well? i guess that is what you would call that. so i adjusted that and set the protrusion to about .03 protrusion and fired it on some once fired cases that are not live except for the primer and it looks like a good dent in the primer so i might see if i can find some time to load up about 100 and try it out. i guess if it is puncturing the primers i can always back it off some. but at least this way i will be guaranteed the round going off and not hearing that horrible click when i have my rifle on a coyote or deer.

  11. #11

    Re: firing pin protrusion

    First off, you are never going to "puncture" a primer no matter what the protrusion is set at, unless of course the pin tip has a sharp point.
    The tip of the firing pin will never indent the primer over about .025". It will bottom out on the anvil of the primer. Typically the protrusion is set from the factory at about .055", which is plenty long and all it does is limit the firing pin travel, giving less impact energy. .035" is optimum.
    "As long as there's lead in the air....there's still hope.."

  12. #12
    klayton83
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    Re: firing pin protrusion

    thank you sharp shooter. i am guessing that this is fred a sss wow it is hard to get ahold of you. i guess that this forum is a better way to do it?

  13. #13
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    Re: firing pin protrusion

    For what it's worth: The firing pin threads (at least the large diameter one that is in pieces on my workbench) are 28 TPI.

    By doing the math, we find that when you adjust the firing pin, each quarter turn of adjustment equates to a change in protrusion (either more or less depending upon which way you turn) of 0.00893"

    One full revolution equates to a change in firing pin protrusion of 0.035714"

    All the best,
    Thomae
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  14. #14
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    Re: firing pin protrusion

    So could u strip down the firing pin and when you reassemble it, only screw it back on one turn or so and have the "optimum" firing lin protrusion? Ive never attemtped to disassemble one........yet......

    Brian

  15. #15
    nsaqam
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    Re: firing pin protrusion

    Quote Originally Posted by airaddict
    So could u strip down the firing pin and when you reassemble it, only screw it back on one turn or so and have the "optimum" firing lin protrusion? Ive never attemtped to disassemble one........yet......

    Brian
    Nope.

    Once you get the FP flush with the boltface THEN you can screw it in one more turn to get ~.035" protrusion.

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