What causes case not fitting gauge?

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  • Confederate
    Bloodstained
    • Nov 2014
    • 28

    #16
    No, they do not fit after resizing. That is the whole point and issue of this post.

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    • Klem
      Chieftain
      • Aug 2013
      • 3509

      #17
      Mine don't fit the Sheridan gauge after resizing either, but not as severe as yours.

      Sheridan gauges are reamed with chamber reamers, the same you use on a barrel. Other manufacturers ream their gauges slightly wider in diameter so all cases fit, and what you end up measuring is longitudinal headspace only. With Sheridan you are measuring longitudinal and axial headspace to a diameter that might be tighter than your chamber. The more important measurement is longitudinal because this is where the risk of case separation comes from. If the case doesn't pass axial headspace as you drop it in you won't be able to measure longitudinal headspace. This is probably why other manufacturers ream their gauges a little wider in diameter than a standard chamber.

      If your sized cases don't fit in the Sheridan gauge but do fit in your gun's chamber then that's OK. Whoever machined that chamber made it a bit sloppy. You will need to find another way of measuring longitudinal headspace - the distance between the middle of the shoulder and the end of the case. The Hornady/Stoney Point gauge will work. You will also need to make sure you don't squeeze the case too much and they won't last long.

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      • VASCAR2
        Chieftain
        • Mar 2011
        • 6219

        #18
        I have a Sheridan case gauge and have experienced the same issue a few years ago. I tried to alleviate the problem by screwing my Hornady die a little deeper but this didn't resolve the issue but I ruined a couple pieces of brass. The thicker Lapua 6.5 Grendel brass seems to do this more than Hornady 6.5 Grendel brass. The cases that exhibit this issue I test in my barrels chamber. I have yet to loose a piece of Lapua or Hornady brass due to the neck cracking or loose primer pockets but I have ruined a couple cases during sizing because of my ignorance.

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        • LRRPF52
          Super Moderator
          • Sep 2014
          • 8569

          #19
          Don't use a case gauge. Use a headspace comparator. That way you can get 3 primary measurements:

          What the shoulder datum location is on factory ammo

          What the shoulder location is on fired brass in a particular chamber

          How much you need to move the shoulder back to achieve reliable lock-up with your chamber when re-sizing.

          I've let this get away from me before and ended up with many cartridges that won't even chamber in a bolt gun with a lot of force camming down on the handle.

          If I would have used the comparator, it would have been easily avoidable when sizing brass. I now check every piece when I size it instead of % batch testing.

          The properly-sized ammo drops in and out of my chambers and a bolt without an ejector in it locks up easily in them with the cartridges.

          For me, I found that I need to move my shoulder back .006" to achieve reliable chambering on several barrels.
          NRA Basic, Pistol, Rifle, Shotgun, RSO

          CCW, CQM, DM, Long Range Rifle Instructor

          6.5 Grendel Reloading Handbooks & chamber brushes can be found here:

          www.AR15buildbox.com

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          • Confederate
            Bloodstained
            • Nov 2014
            • 28

            #20
            Awesome information! Thank you so much gentlemen. I'll get back at it again taking your instruction to practical application.

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            • Klem
              Chieftain
              • Aug 2013
              • 3509

              #21
              I was thinking about this situation and took some photos to show what I mean...



              The length below each photo is from a Stoney Pt/Hornady headspace gauge. 52' is right, you just can't get precise information from a rifle gauge alone. I use them as more quick, ready-reckoners when clunking away on the press.

              You can see from the photo that the only time these Lapua cases fit properly into the Sheridan is when they are brand new/unfired. They then stretch a whopping .02" in my chamber. From then on they will only expand and contract .004" until they are discarded. I prefer a .004" bump however some are more and some are less. They are never all exactly the same so I measure a few to get an average. This one was less at .003" but will still reliably function. If you look at the right hand photo even after sizing I can't use the information levels Sherridan has shaved into the top. The sized case sits slightly proud of the top. My Lilja chamber is larger than Sherridan's reamer which is a pity.

              In your situation there seems to be a lot of diameter expansion going on. If the first firing of a factory case does not blow up in your face then after that as long as you size them back only .003 - .006" you will maximise their life, guarantee reliability and frankly be as safe as you can.

              It could also be that your loads are too hot. I've seen this happen in 223. Sizing dies don't size the whole length of the case so while you squeeze most of the case the web down the bottom is left alone. Hot loads will migrate the brass to fill all available space in both the chamber and bolt when it goes off. Even bleeding into the gap where the extractor sits. You then have to spin the case in a drill press while holding a fine file against the bottom of the case. Shave a bit of the brass off at a time until it fits the gauge and reconsider your loads.
              Last edited by Klem; 08-19-2017, 02:01 PM.

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