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Thread: Form-1 can over bore allowance?

  1. #1
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    Form-1 can over bore allowance?

    I googled a little bit and didn't find the answer.

    I'm planning a form-1 can and was wondering how much overbore is allowed?

    What I'm saying is, typically, for a .30 caliber suppressor it is common to use a 3/8" drill bit.

    So, when you put caliber on the form-1, you list 30 caliber, even though the hole is physically .375"

    All manufacturers use over bore to avoid problems with concentricity and instability.

    But the ones I have all list the intended caliber on the markings.

  2. #2
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    However much you want. No one is going to measure your work.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

  3. #3
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    Quote Originally Posted by markm View Post
    However much you want. No one is going to measure your work.
    Thanks. I suspected as much. Appreciate the feedback.


    Sent from my iPhone using Tapatalk

  4. #4
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    I think you give it a caliber designation, but the bore can be whatever you want. When we did Pappabear's F1 can, I just matched up a drill bit to a factory can.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

  5. #5
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    Quote Originally Posted by markm View Post
    I think you give it a caliber designation, but the bore can be whatever you want. When we did Pappabear's F1 can, I just matched up a drill bit to a factory can.
    Yeah, I think it sounds like the caliber you list is basically the minimum diameter.

    Like, as long as it can do what you claim it can do, it should be fine.


    Sent from my iPhone using Tapatalk

  6. #6
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    Yep. If I did another kit can I'd just designate it as 7.62 even if it was a 5.56 project.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

  7. #7
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    I put .22 on form 1's for everything. It doesn't matter what size the bore is, or how it's threaded, .22 will go through it.

  8. #8
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    Quote Originally Posted by markm View Post
    However much you want. No one is going to measure your work.
    This.

    In 20 years of shooting NFA stuff, not once have I seen or even heard a rumor of an engraving/paperwork spot check/issue.

  9. #9
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    For 300 BLK I put 30 in the caliber section.

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