Grendel Build: Possible Headspace Issues

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  • 8Gauge
    Unwashed
    • Dec 2016
    • 13

    Grendel Build: Possible Headspace Issues

    Hi all,

    I recently built a Grendel AR, and yesterday I tested the weapon. I used all handloads, and velocities I documented were all very close to what my reloading data (Barnes) said they would be- leading me assume initially that things were off to a good start. However, I began to notice that virtually all of my shell casings had a polished ring on the case body above the head. Many cases also exhibited extruded primers, flattened primers, and even a few punctured primers. The weapon has an Odin Works 18" barrel and a Maxim Firearms bolt with a recess of 0.136". I did a lot of work trying to make sure I had my ducks in a row for this build, but the shell casings make be worry... All brass shown in images is Hornady brass, once fired (new). Any input or experience with similar issues would be greatly appreciated!

    - 8Gauge
  • Bigs28
    Chieftain
    • Feb 2016
    • 1786

    #2
    Your attachments are not working for me when I click on them.

    Comment

    • 8Gauge
      Unwashed
      • Dec 2016
      • 13

      #3
      Photos

      IMG_4997.jpgIMG_4999.jpgIMG_4994.jpgIMG_4993.jpg

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      • VASCAR2
        Chieftain
        • Mar 2011
        • 6219

        #4
        There is a post on this page in regards to an Odin barrel chamber which might be out of spec. If you haven't read this thread review it and inspect the chamber in the recommended manner.


        Just installed a Odin works 20" 6.5 Grendel . Just went to shoot it and Hornady sst and federal 90gr varmint brass bulged the hole length of the case except a mil or 2 by the primer end and is sticking so bad we can barely pull it out with charging handle ( won't gas eject ). We done the method of checking the chamber by



        There has also been issues where the tail of the 6.5 Grendel bolts were to short which permitted the firing pin to protrude to far and pierce primers. I think the bolts might have been Odin but I can't remember for sure. The bolt should measure .281 from the rear of the tail to the face of the bolt/lugs. If the barrel passes the test and the bolt and firing pin are in spec has the barrel been shot with factory ammo.

        Since these are reloads I'd suggest you fire some factory ammo like Hornady 6.5 Grendel. If the problem only exist with your hand loads your ammo could be to hot or you may have the bullets seated to long into the lands. I'm not sure if you can set the shoulder back to far when resizing to cause the problems your experiencing. If the factory ammo pierces primers like your handloads I would discontinue use and either get the head spaced checked or contact Odin. You can rent go no go chamber gauges.

        The light ring just above the base of the brass is common on resized 6.5 Grendel brass.
        Last edited by VASCAR2; 06-20-2017, 01:48 AM.

        Comment

        • 8Gauge
          Unwashed
          • Dec 2016
          • 13

          #5
          Thanks, VASCAR2. I will be taking it to a gunsmith soon, I think. The brass shown in the picture has never been put through a die- it is new Hornady brass. That's why the rings were making me nervous. I see those rings on my 30-06 all the time after reloading, but the 6.5 casings are new. I will take your advice on shooting some factory 6.5 ammo. The barnes bullets I loaded did seem a bit long, but I couldn't see any signs of the lans kissing the copper after loading and unloading unfired rounds. RE your comment about the bolt length: if I use calipers to measure that length, do I measure from the very rear (tail) of the bolt to the forward most face? I guess thats essentially the entire length of the bolth piece itself... I'm unclear about where .281" comes from. Thanks for the info!

          Comment

          • 8Gauge
            Unwashed
            • Dec 2016
            • 13

            #6
            I think I got it- I measure my bolt at 2.81" long.

            Comment

            • VASCAR2
              Chieftain
              • Mar 2011
              • 6219

              #7
              Yes, from the very end of the tail length wise to the top of the bolt. With a bolt shorter than .281 a firing pin can protrude deeper into the breach face.

              Comment

              • Lastrites
                Warrior
                • Apr 2017
                • 678

                #8
                I would also measure the firing pin protrusion, if you by chance happen to have received an enhanced firing pin for 7.63x39 or firing pin that was just out of spec.

                Comment

                • LRRPF52
                  Super Moderator
                  • Sep 2014
                  • 8569

                  #9
                  Originally posted by 8Gauge View Post
                  I think I got it- I measure my bolt at 2.81" long.
                  That's the correct Grendel bolt length. Looking at your punctured primer picture, I see that the edge of the primer is very round.

                  That leads me to believe you have a mechanical issue with the firing pin length, or the firing pin aperture being too large, or both.

                  Either way, it's an unsafe condition with piercings like that.
                  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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