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Long Contact Points for Test Indicator

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  • Long Contact Points for Test Indicator

    Help me out with this - I typically use a 2.5" contact point on a Interapid .0001" test indicator when dialing in rifle barrels to be chambered. I also have a 1.5" contact point for a B&S .0001" test indicator, and like to use it on barrels that will be chambered for short cartridges (6PPC, 6BR, etc.). How does one figure the actual amount of runout with these longer points - is the indicator more sensitive, or less than what I see on the dial when using a longer point?

  • #2
    It would be less sensitive. .0001 indicated movement would actually be greater, by how much depends on the difference in length and the angle of travel.
    North Central Arkansas


    • #3
      If I'm understanding the question correctly, on any given indicator a longer point would make the indicator less sensitive. For a given displacement of the point, it will move through a smaller angle. This assumes you're comparing two different-length points on the same indicator. On different indicators, who knows; it would all depend on how the rest of the indicator linkage is proportioned.

      As far as what the actual measurement is...that type of indicator isn't really made for measuring. They're for doing a relative comparison.
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