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Thread: SAAMI tolerance question

  1. #1

    SAAMI tolerance question

    I am used to seeing tolerances given in plus or minus, but it looks like SAAMI specifies one extreme dimension and then adds or subtracts a tolerance. Is my understanding correct?

    For instance, when they call out 0.035+0.010 -- that means 0.035 to 0.045 is acceptable, correct? And right below "0.050-0.010" means 0.040 to 0.050 is acceptable?

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  2. #2
    Yes.
    You can see that ammo usually has only a minus tolerance, the spec is for a maximum dimension.
    Chambers have only a plus tolerance, the spec is for a minimum chamber.
    This ensures that a minimum chamber will accept a maximum round.

    Dimensions of rim and extractor groove are toleranced plus or minus to ensure a good grip by the extractor.
    Code Name: JET STREAM

  3. #3
    Thanks! Is there a tolerance for runout?

    I'm looking at some new WWB that has been giving me extraction issues and it looks like the recessed part of the casing (the section called out as .347-.020) is not perfectly centered so instead of having a symmetrical 0.023" thick rim for the extractor to grab on to, I might have 0.018 on one side and 0.028" on the other

  4. #4
    Not on the drawing. That is really some sloppy brass, though. I'd send some to WW and see what they said.
    Code Name: JET STREAM

  5. #5
    Quote Originally Posted by 0ddl0t View Post
    Thanks! Is there a tolerance for runout?

    I'm looking at some new WWB that has been giving me extraction issues and it looks like the recessed part of the casing (the section called out as .347-.020) is not perfectly centered so instead of having a symmetrical 0.023" thick rim for the extractor to grab on to, I might have 0.018 on one side and 0.028" on the other
    Quote Originally Posted by Jim Watson View Post
    Not on the drawing. That is really some sloppy brass, though. I'd send some to WW and see what they said.
    I've had two issues with bad Winchester brass that wouldn't chamber. One box was .38 Special practice ammo, the other was a spendy box of .357 Silvertip. In both cases, the cases had issues where they were malformed and wouldn't chamber.

    Winchester told me they would issue me a shipping label, and upon receipt and determination that there was something wrong, compensate me in some way for the unused ammo.

    Since I'd shot most of the Silvertips before I figured out it was the ammo and not dirty chambers, and there were only a couple of rounds affected in the box of .38, I didn't bother and just put Winchester on my list of "do not buy" along with cheap Russian stuff.

    I wonder if they are having systemic issues with making brass.
    I was into 10mm Auto before it sold out and went mainstream.

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