Hornady OAL gauge vs. DIY Fired case - .03 difference

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  • Sticks
    Chieftain
    • Dec 2016
    • 1922

    Hornady OAL gauge vs. DIY Fired case - .03 difference

    I've been trying to get an accurate measurement for the lands on my Barlitien barrel (AR15 upper), so I started with taking a fired case, bumping the shoulder back .003 and busing sizing the neck ever so slightly to hold a bullet enough to be pushed in with moderate pressure, but still hold relatively firm.

    After 8 attempts or so cambering and making sure the bolt goes into battery, then using a cleaning rod to help push the case out (making sure the bullet is not jammed in the lands) I got 4 readings that were 1.711 - case head to ogive on a 123 ELD.

    Doing the same with a Hornady OAL gauge, I get 1.681. That is a huge difference. I would have expected the fired case to be shorter, not longer, but that is going off the bolt rather than the case being shoved all the way into the freebore.

    I measured some Horandy American Gunner and it measures 1.695 (ELD is 1.660). When I chamber the HAG ammo, it does not jam in the lands, and the measurement does not change, no marking on the bullet. According to the Hornady tool that should be jamming into the lands.

    Where am I screwing up that I can not verify my measurement with the tool vs the DIY fired case? I am trying to figure out what my jump to lands should be since when I am loading ELD to mag length (2.266 +/-.002) 1.696 to ogive ~ .005 off the lands based on my DIY fired case. This might explain the pressure signs on reloaded ammo significantly below what others are using as safe.
    Sticks

    Catchy sig line here.
  • grayfox
    Chieftain
    • Jan 2017
    • 4295

    #2
    Good morning Sticks,
    I can't speak to the use of the OAL gauge, I use your fired case method/ slightly resized (the 0.003 that you mention, I use 0.005-6 but that's just me) and of course unprimed. The wrinkle for me is that I put a bit of light oil or graphite inside the case mouth, then seat the bullet a little too long, shorten it up successively until I get no push-back from the chamber (note this may take more than one bullet so the ogive area stays clean for you). If there's resistance I don't try to force it in, that tells me it's too long for the chamber. use collet puller or skinny rod to poke the bullet out and try again... or have 3-4 all set up to ever shorter lengths by 0.010 or so...
    By shortening I get a good sense of which one will just clear the lands.
    O yeah, when inserting/extracting I just seat the bullet in the extractor then push in against the ejector, use my fingers and bcg (manually) to guide it into or out of the chamber, (using the upper+bcg only) that way no forces act on the bullet to change its location other than the chamber itself.

    Also, I haven't tried the eldm's or ssts to go mag length they seem to run better < 2.260, down to about 2.245 for me. Maybe the hornady's do not need to be so close to the lands, as say the berger's seem to be.
    "Down the floor, out the door, Go Brandon Go!!!!!"

    Comment

    • LRRPF52
      Super Moderator
      • Sep 2014
      • 8569

      #3
      Fired cases are longer because they expanded into the chamber, which is larger.

      Even with rebound from obturation, they are still larger, because they are extracted from the chamber before they are able to heat-sink over to the chamber walls.

      This is why brass is hot when it ejects from a self-loader, and why it is relatively cool from a bolt gun.

      As to base-to-ogive length, I personally only use dummy cartridges and not the gauge. Not saying that's the right way, just what I prefer.

      I load my dummy cartridge long, color the ogive with a black marker, and see if it chambers with finger pressure.

      If not, I seat it a little deeper, then re-color and chamber.

      I prefer it to fall free from the chamber, and I won't even install a barrel unless it chambers and freely allows several factory loaded cartridges to drop free.

      It makes no sense for my uses to load longer than magazine-allowable COL, so I start at 2.300" and work back from there, unless the bullet has such a tangent ogive that has consensus load data putting it in the 2.200" COL or less lengths, which is common with many of the lighter 6.5mm varmint projectiles.
      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

      Comment

      • RiverRider
        Warrior
        • Oct 2017
        • 104

        #4
        The best way I know to figure out the zero-to -lands length is to use a fireformed and properly resized case with the neck split longitudinally with a dremel cutoff wheel. Insert your bullet barely into the case and chamber the case. Carefully extract and measure with a comparator. Repeat to verify. Works like a charm.

        Comment

        • Klem
          Chieftain
          • Aug 2013
          • 3509

          #5
          Sticks,

          When you say you compare it with the Hornady OAL gauge do you mean the gauge with the supplied modified Grendel case like this in the photo?

          Comment

          • Sticks
            Chieftain
            • Dec 2016
            • 1922

            #6
            Originally posted by Klem View Post
            Sticks,

            When you say you compare it with the Hornady OAL gauge do you mean the gauge with the supplied modified Grendel case like this in the photo?
            [ATTACH=CONFIG]10319[/ATTACH]
            Yup.

            Right now the Hornady gauge is telling me that my lands are 1.681, but Horandy American Gunner which is 1.695 is not touching the lands when chambered.

            Short of taking a casting of my chamber, I am not sure what to do. I am sure there is a simple math formula that I need, but nothing is making sense right now.
            Sticks

            Catchy sig line here.

            Comment

            • Drillboss
              Warrior
              • Jan 2015
              • 894

              #7
              Originally posted by Sticks View Post
              Yup.

              Right now the Hornady gauge is telling me that my lands are 1.681, but Horandy American Gunner which is 1.695 is not touching the lands when chambered.
              Did you get the 1.681 measurement with an ELD-M bullet, or with the HAG bullet? The ID of Hornady comparator bushing is about 0.254" so it's really not measuring the base to ogive, it's base to that point on the bullet profile that matches the ID of the bushing.

              Comment

              • Sticks
                Chieftain
                • Dec 2016
                • 1922

                #8
                Both the DIY and the Hornady case gauge were done with 123gr ELD.

                Was I mistaken that the bullet comparator bushing was the ogive measurement?
                Sticks

                Catchy sig line here.

                Comment

                • Klem
                  Chieftain
                  • Aug 2013
                  • 3509

                  #9
                  I don't think you are doing anything wrong...In fact it sounds like you are being very precise and correct with your measurements. The discrepancy is the Hornady modified case is a different length to your fire-formed/sized cases.

                  From the shoulder forward to the ogive they will both be the same distance (if using the same bullet) but you are measuring the whole length of the case as well; from the base to the ogive. Your fired cases expand to the full length of the chamber, and then retract slightly because brass is designed to be elastic to permit extraction. You then bumped the cases shorter by .003. The modified Hornady case from the factory will be full length sized, to SAAMI specs, which is even shorter. The more precise way for your gun is to use your fire-formed and sized cases. The Hornady tool (which I also use) is less precise.

                  The second issue with the American Gunner is a good example of this. If you measure from the shoulder forward to the ogive you will find that Amercian gunner is shorter than your lands by a certain amount. The problem is we don't measure from the shoulder forward, we are measuring from the base of the case forward, and the cases are two different lengths.

                  Comment

                  • Effenpig
                    Unwashed
                    • Nov 2017
                    • 9

                    #10
                    Originally posted by Sticks View Post
                    Yup.

                    Right now the Hornady gauge is telling me that my lands are 1.681, but Horandy American Gunner which is 1.695 is not touching the lands when chambered.

                    Short of taking a casting of my chamber, I am not sure what to do. I am sure there is a simple math formula that I need, but nothing is making sense right now.

                    To account for the difference in the Hornady case and a case fired from my chamber i like to measure each with the .350 bushing so I have a baseline

                    So if the cases from my chamber are say .003" longer I know to add that amount when I use the hornady case to take a measurement

                    Hope that makes sense

                    Comment

                    • Drillboss
                      Warrior
                      • Jan 2015
                      • 894

                      #11
                      Originally posted by Sticks View Post
                      Both the DIY and the Hornady case gauge were done with 123gr ELD.

                      Was I mistaken that the bullet comparator bushing was the ogive measurement?
                      The "ogive" diameter would be 0.264" with SAAMI tolerance of -0.003". I was having similar confusion a couple years ago and finally called Hornady and got someone to find the actual specs on those bushings. He told me the 26 bushing ID is 0.265".

                      I colored a 123gr SST bullet and eased it into the throat until I got scuff marks from the lands. The comparator bushing contacted the bullet well forward of those marks. I think JASmith started a thread on here about this when we were having that discussion. Found it: http://www.65grendel.com/forum/showt...ator-vs-Throat

                      Bottom line, the Hornady Overall Length Gage is a great tool, but the measurements that it gives you are specific to the bullet type that you're measuring.
                      Last edited by Drillboss; 12-03-2017, 02:31 PM. Reason: Found the old thread

                      Comment

                      • Sticks
                        Chieftain
                        • Dec 2016
                        • 1922

                        #12
                        Originally posted by Drillboss View Post
                        The "ogive" diameter would be 0.264" with SAAMI tolerance of -0.003". I was having similar confusion a couple years ago and finally called Hornady and got someone to find the actual specs on those bushings. He told me the 26 bushing ID is 0.265".

                        I colored a 123gr SST bullet and eased it into the throat until I got scuff marks from the lands. The comparator bushing contacted the bullet well forward of those marks. I think JASmith started a thread on here about this when we were having that discussion. Found it: http://www.65grendel.com/forum/showt...ator-vs-Throat

                        Bottom line, the Hornady Overall Length Gage is a great tool, but the measurements that it gives you are specific to the bullet type that you're measuring.
                        At this time, all I plan on using is the 123 ELD. I plan on using the same tool for all my loading, so I just need to find out where my lands are at from the bolt face. I have a feeling that there is a little headspace thing going on here that is causing some of my issues since my DIY was done from the bolt face, and the Hornady gauge was pushed in as far as it would go.

                        I'll have to measure it again when I get home, but I think the Hornady modified case measured 1.122, and my sized case is 1.118 to the shoulders.

                        Sounds like I need to do the sharpie thing on the bullet and rinse and repeat.
                        Sticks

                        Catchy sig line here.

                        Comment

                        • RiverRider
                          Warrior
                          • Oct 2017
                          • 104

                          #13
                          I tbi k you're right about that, and you can verify the headspace difference between the Hornady modified case and one of your working fireformed cases using a .30-cal comparator insert with your compartor tool. You WON'T be getting the absolute headspace measurement, but it does not matter, a relative measurement will reveal the difference.

                          Comment

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