Brass growth Question

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  • Unclered
    Bloodstained
    • Sep 2016
    • 29

    Brass growth Question

    I haven't noticed this in reloading other caliber rounds. My 6.5 Grendel hornady cases vary in length from 1.512 to 1.532. Book says 1.515 to 1.525. Strange? none were loaded hot. All reasonable research. 3 diff powders, CFE, 8208, & 4895. Sadly, I didn't separate.
    "It's a long shot with a limb in the way but it beats suckin' pond water"- Jed Clampit 1964
  • Lone Hunter
    Warrior
    • Jan 2017
    • 170

    #2
    Mine have been from 1.510 to 1.524. Will trim to 1.515 and not worry about it. Haven't checked the new Hornady brass to see where it measures at. Is this fired out of an AR or Bolt gun. Reason I ask is now I have both and wonder if the brass will grow faster out of one or the other.

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    • Unclered
      Bloodstained
      • Sep 2016
      • 29

      #3
      ar. all out of the same rifle. same throat
      "It's a long shot with a limb in the way but it beats suckin' pond water"- Jed Clampit 1964

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      • Bigs28
        Chieftain
        • Feb 2016
        • 1786

        #4
        I had the same thing from my ar with factory loads sst, amax, and eldm. Brass ranged in size from 1.510-1.53+

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        • Kilco
          Chieftain
          • Jan 2016
          • 1201

          #5
          Trim it all once and don't worry about them again until you reach 1.530 length... even then all chambers are different.

          I find the Grendel to be very forgiving on brass. I get 5-6 firings with a max charge of 8208 before I have to even think of trimming again.

          Comment

          • JASmith
            Chieftain
            • Sep 2014
            • 1620

            #6
            There may be wisdom in measuring the distance from bolt face to start of throat. The 1.530" dimension sounds awfully close to the SAAMI minimum chamber length.

            Two things happen when the stuff stretches enough to engage the start of the tnroat. Neither are good.

            The first is that one may start seeing more frequent failures to go into battery, or difficulty in closing the bolt.

            The second is that if those warning signs are ignored the brass has nowhere to go when it should expand to allow the bullet to slide out on firing. That added clamp force can increase pressures by more than 5,000 psi.

            If memory serves, the 1.525" recommended case length gives .005 to .007" clearance to assure no contact with the SAAMI minimum throat start.

            PS I disvovered this after 10-15 firings with full length size each time.

            PPS. I'll check these numbers when I get back to my desk or someone who has the SAAMI dimensions handy jumps on the numbers first. I will edit as needed.

            Edit

            My copy of the SAAMI drawing shows the chamber neck dropping from 0.3000" to 0.2644" at 1.530" from the breech. These are the minimum dimensions. The max length is 0.015" longer.

            The
            maximum cartridge length per SAAMI is 1.520" with the minimum being 0.020" shorter.
            Last edited by JASmith; 10-11-2017, 01:19 AM. Reason: Clarify SAAMI dimensions
            shootersnotes.com

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            • StoneHendge
              Chieftain
              • May 2016
              • 2009

              #7
              Is that before or after sizing and have you checked your brass with a comparator or Wilson case gauge? I have one barrel where the rear grows .01" and its .005" on my JP.
              Let's go Brandon!

              Comment

              • kmon
                Chieftain
                • Feb 2015
                • 2095

                #8
                Originally posted by JASmith View Post

                Edit

                My copy of the SAAMI drawing shows the chamber neck dropping from 0.3000" to 0.2644" at 1.530" from the breech. These are the minimum dimensions. The max length is 0.015" longer.

                The
                maximum cartridge length per SAAMI is 1.520" with the minimum being 0.020" shorter.
                That is the way I read the specs as well Mr. Smith. One could trim to 1.50 and still be at SAAMI min spec and not have to worry about trimming for a long time at the rate Grendel brass grows which is slow compared to some of the other calibers I reload.

                Comment

                • Unclered
                  Bloodstained
                  • Sep 2016
                  • 29

                  #9
                  Thanks gentlemen
                  "It's a long shot with a limb in the way but it beats suckin' pond water"- Jed Clampit 1964

                  Comment

                  • Mad Charlie
                    Warrior
                    • May 2017
                    • 827

                    #10
                    The way I approach this, is to determine the exact chamber length in my barrels, and make sure that the case is .005 shorter than my shortest chamber.
                    Personally, I don't want to give up any more neck length than I have to. It has been my experience (admittedly limited) so far, that my Grendel chambers have quite a bit of room to let cases grow and it might take a number of firings before there is any problem. I like to have all my cases the same length (after sizing) but some of them need to "catch up" before trimming to as long as I can.

                    All chambers are a little different and kits consisting of a plug that you seat overlength in a shortened case and then chambering and measuring with calipers, are available.
                    Last edited by Mad Charlie; 10-15-2017, 05:18 PM.

                    Comment

                    • Lone Hunter
                      Warrior
                      • Jan 2017
                      • 170

                      #11
                      Originally posted by Mad Charlie View Post
                      The way I approach this, is to determine the exact chamber length in my barrels, and make sure that the case is .005 shorter than my shortest chamber.
                      Personally, I don't want to give up any more neck length than I have to. It has been my experience (admittedly limited) so far, that my Grendel chambers have quite a bit of room to let cases grow and it might take a number of firings before there is any problem. I like to have all my cases the same length (after sizing) but some of them need to "catch up" before trimming to as long as I can.

                      All chambers are a little different and kits consisting of a plug that you seat overlength in a shortened case and then chambering and measuring with calipers, are available.
                      Yes, you can get the chamber plugs a Brownells or Sinclair. They are about $6.95 a piece

                      Comment

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