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Thread: Firing pin tip shape

  1. #1
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    Firing pin tip shape

    Is there a proper radius size for a firing pin tip? From what I remember, it isn't suppose to be a complete radius (half ball shape) but a larger radius then half the tip diameter.

  2. #2
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    Recently, I have started shaping the firing pin tip to kind of a cone with a radius. This for larger pins (like the post 64 Model 70). I started doing this in an attempt to prevent blanking without bushing the firing pin hole. It seems to work. The cone commences at the bolt face (with the pin protruding) and tapers down to 1/16 inch about .030 from the end. Regards, Bill.

  3. #3
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    Quote Originally Posted by Bill Leeper View Post
    Recently, I have started shaping the firing pin tip to kind of a cone with a radius. This for larger pins (like the post 64 Model 70). I started doing this in an attempt to prevent blanking without bushing the firing pin hole. It seems to work. The cone commences at the bolt face (with the pin protruding) and tapers down to 1/16 inch about .030 from the end. Regards, Bill.
    Hey! That's not bad!

    I'da' never thought of it but in retrospect the stretched cone is much stronger, takes gas impingement better and virtually eliminates the stress riser and fatigue generated by the typical forward/back folding action of the typical garbage-can-lid blank.....you could actually "pierce" a primer with your arrangement and it'd self-heal LOL!!!

  4. #4
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    Brother Bill Leeper is just a great font of knowledge.

  5. #5
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    When a cartridge is fired, do you think that the firing pin reaches its full extension from the bolt face? Perhaps the issue is how far back the shape extends before it reaches the maximum diameter. Just a thought...

  6. #6
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    Was a time when the recommendation was a flat face and a radius around pin diameter, but I recall that design was to still hit the primer anvil while compensating for the tolerances in manufacture.

  7. #7
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    Quote Originally Posted by Boyd Allen View Post
    When a cartridge is fired, do you think that the firing pin reaches its full extension from the bolt face? Perhaps the issue is how far back the shape extends before it reaches the maximum diameter. Just a thought...
    Well.... I have a lot of Remingtons and I will be trying the cone-shaped tip I think

  8. #8
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    I had severe blanking with a newer M70 and a 6x47 Lapua (srp). With mild starting loads it still blanked primers. The radius on that firing pin tip did in fact retreat too far into the bolt face when firing and sheared perfect circles out of 90% of the primers fired. I ended up bushing it and turning down to .067 or so and never a problem afterwards.

  9. #9
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    I had a discussion with Ed Shilen about tip shape back in the 80's. What he said made sense. Flat with a very small radius on the edges which reduces cratering and helps reduce piercing.

  10. #10
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    Quote Originally Posted by msalm View Post
    I had severe blanking with a newer M70 and a 6x47 Lapua (srp). With mild starting loads it still blanked primers. The radius on that firing pin tip did in fact retreat too far into the bolt face when firing and sheared perfect circles out of 90% of the primers fired. I ended up bushing it and turning down to .067 or so and never a problem afterwards.
    I wonder how much is too much. Most actions have nominally .050-.060 protrusion and .250 pin fall. So roughly .200 pin retraction on "most" actions.
    I have to say that I don't think this is what causes piercing or maybe I'm misunderstanding your post.

  11. #11
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    Quote Originally Posted by mwezell View Post
    I wonder how much is too much. Most actions have nominally .050-.060 protrusion and .250 pin fall. So roughly .200 pin retraction on "most" actions.
    I have to say that I don't think this is what causes piercing or maybe I'm misunderstanding your post.
    Swap ogive for radius & it seems logical.

  12. #12
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    Quote Originally Posted by John Kielly View Post
    Swap ogive for radius & it seems logical.
    Lol! It does. I has missed read the post. My apologies.

  13. #13
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    I finally found what I thought I had seen. Bob Dunlap...

    https://www.milsurps.com/showthread.php?t=49179

    Part 2 talks about shape and reasons why.
    Last edited by Rflshootr; 12-03-2019 at 10:17 AM.

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