6mm Grendel Group Design Project

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  • BluntForceTrauma
    Administrator
    • Feb 2011
    • 3897

    6mm Grendel Group Design Project

    Gentlemen, Warriors, and Vile Masses of The Horde: Let’s put our heads together and spec out the ultimate 6mm cartridge based on the Grendel case. Release of the new .224 Valkyrie got me thinking about Grendel-based wildcats. I think 6mm is begging to be a factory round.

    Robert Whitley’s 6mmAR Turbo is very, very close.

    I already have in mind my perfect 6mm round. I challenge you guys to do better.

    Hopefully, some enterprising ammo maker will be impressed with our findings and create a factory round. Don’t worry about your ideas being “stolen." There is no money in wildcat cartridge design. The money is in the manufacturing — making and selling factory ammunition and firearms. So, unless you’re Remington, Winchester, or Hornady, feel free to take a stab at it.

    Parameters: (1) Round must fit within the dimensions of a standard AR magazine allowing a cartridge overall length (COL) of 2.260 to a max of 2.300”. (2) Cartridge must double-stack in said magazine, to maximize firepower while still feeding reliably.

    OK, here’s my thinking. . . .

    Start with a Grendel case, which has a case length of 1.520" or 38.6mm.

    Next, take the bullet with the longest nose length that you intend to use: the gorgeous Berger 6mm 105 Hybrid with a nose length of 0.701”.

    Even though some magazines allow a COL of 2.300, let’s hedge a bit for the sake of reliable feeding and declare our max COL to be 2.290. (Factory loads with shorter bullets could be loaded to standard AR COL of 2.260.)

    Now, COL of 2.290 minus bullet nose length of 0.701 equals a max case length of 1.589. Let’s just round it to 1.590" or 40.4mm.

    THUS, WE NEED A BRASS MANUFACTURER TO INCREASE LENGTH OF GRENDEL CASES FROM 38.6MM TO 40.4MM!

    Neck length of this brass will be on the short side for more case capacity, but should match the proven 6mm BRX of .210”.

    Shoulder remains at 30 degrees, for feeding reliability. I just don’t trust 40 degrees for feeding from the magazine in an AR; I could be wrong, but that’s my opinion as of today without further proof.

    From a 24” barrel this case should launch the Berger 6mm 105 Hybrid at about 2850 fps. Other, lighter 6mm bullets will be even faster.

    Why not the 6.8 case cut down and necked down? Not as fat as a Grendel case, thus lacks capacity, thus lacks velocity.

    Why not 6mmBR brass with a 0.473 case head? Doesn't double-stack in an AR magazine!

    The 6mmAR Turbo case is pretty much it, except that it’s based on existing Grendel brass at 38.6mm. If a manufacturer would make that case but with a slightly longer length of 40.4mm, we’d be golden.

    Thoughts from The Horde?
    :: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets

    :: I Drank the Water :: Revelation 21:6 ::
  • LRRPF52
    Super Moderator
    • Sep 2014
    • 8569

    #2
    A SAAMI spec 6mm Grendel with brass and ammo would be the cartridge to beat in the AR15 for LR, especially with some of the new magazines that are coming out.

    What's the ogive length on the 110gr Sierra Match King?

    Here are some baseline 6mm projectiles for comparison:

    Last edited by LRRPF52; 11-08-2017, 08:31 PM.
    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

    • BluntForceTrauma
      Administrator
      • Feb 2011
      • 3897

      #3
      I emailed Sierra for the ogive length on their new 6mm 110gr but they won't put that info in an email, only over the phone. So I still have to call them.

      UPDATE: Called and called Sierra tech info line yesterday and could not, for the life of me, get a live person to get specs on the 6mm 110.
      :: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets

      :: I Drank the Water :: Revelation 21:6 ::

      Comment

      • JASmith
        Chieftain
        • Sep 2014
        • 1620

        #4
        Also, look at the 107 gr ELD Match by Hornady.
        shootersnotes.com

        "To those who have fought and almost died for it, freedom has a flavor the protected will never know."
        -- Author Unknown

        "If at first you do succeed, try not to look astonished!" -- Milton Berle

        Comment

        • SHORT-N-SASSY
          Warrior
          • Apr 2013
          • 629

          #5
          Great project, BFT ! Now, if we can fit the Sierra 6mm 110-grain BTHP Matchking projectile (BC - 0.617; O.A.L. - 1.340") into the equation, by cutting out the front of the magazine ---

          (https://www.youtube.com/watch?v=TgfxCcK-47k)

          Comment

          • Overwatcher
            Unwashed
            • Mar 2015
            • 10

            #6
            Very interested..I've wondered for years why we haven't seen something in the 6mm dept really take off.Plenty of wilds out there 6 DTI,6X68,243 LBC,6MM AR-Turbo etc....
            I'm putting together a .243 LBC now,Have to see where that goes.
            Digging the ideas BFT

            Comment

            • SDet
              Bloodstained
              • Sep 2016
              • 82

              #7
              If I could get hornady brass and dies, and a barrel for less than $600, I'm in.

              Comment

              • kmon
                Chieftain
                • Feb 2015
                • 2095

                #8
                How about a 35 degree shoulder, should still feed well.

                Comment

                • lrgrendel
                  Warrior
                  • Jul 2013
                  • 662

                  #9
                  Start with the 6mm x 47 LAPUA.

                  Decrease every measurement proportionaly till you get to where you need to be I.E. to be able to double stack and maximum case length....

                  Comment

                  • K_4c
                    Unwashed
                    • Oct 2017
                    • 21

                    #10
                    Bc vs MV

                    The 6 Grendel does not have enough in the boiler room to push the 105-110 class as efficiently as the 95 TMK's. Recoil is noticeably less with the TMK's too.

                    I wish the ar-15 bolt had enough meat on it for a 6br or 22br.

                    All that being said, I have all three Grendel's (6.5, 6 and 224).

                    Factory 6.5 JP 18" drives the 107 smks at 2670 FPS or 120 scenars to 2560 fps

                    McGowen 6 Grendel/20" tube pushes the 105 RDF's 2700 and the 95 tmks to 2810 fps.

                    Lastly, ARP .224AR/20 tube slings the 75 eld's at 3010 FPS (matches most bolt .223ai) and is a joy to shoot inside 500.

                    If I had to pick 1 of the 3, it'd be the 6mm Grendel. 6mm is hard to beat for energy/MV in the small ar platform.

                    Comment

                    • BluntForceTrauma
                      Administrator
                      • Feb 2011
                      • 3897

                      #11
                      Originally posted by K_4c View Post
                      I wish the ar-15 bolt had enough meat on it for a 6br or 22br
                      Sounds like you'd be OK with reduced mag capacity?
                      :: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets

                      :: I Drank the Water :: Revelation 21:6 ::

                      Comment

                      • StoneHendge
                        Chieftain
                        • May 2016
                        • 2009

                        #12
                        There we have it - maybe 6mm Nosler is what it should be Someone get Bend on the line. Just use a Grendel case head please. But I have to confident that whoever designed the head on the 22 Nosler is currently bagging groceries at Food 4 Less.....

                        A 105 RDF with a G7 of .280 going faster than a 90 gr SMK at 2700 out of a 24" with a G7 of .256. Absolutely blows 224 Valkyrie out of the water with both ballistics and delivered energy. And ifthe case could accommodate a little more powder .....

                        K_4c, what sort of load are you using for the RDFs and what is your COAL/jump? I have a 26" McGowan on order and I'm getting all drooly again. The RDFs are the first thing I'm going to try.
                        Let's go Brandon!

                        Comment

                        • K_4c
                          Unwashed
                          • Oct 2017
                          • 21

                          #13
                          Originally posted by BluntForceTrauma View Post
                          Sounds like you'd be OK with reduced mag capacity?
                          To run a 6br (105 hybrids at 2800-2850 FPS), yes. 15-20 rds is fine for me considering the inherent accuracy of the br cartridge. Lapua brass, small primer, perfect burn column and long neck make it a perfect semi auto cartridge.

                          6mm dasher would be great too for the extra Hp.

                          Comment

                          • K_4c
                            Unwashed
                            • Oct 2017
                            • 21

                            #14
                            Originally posted by StoneHendge View Post
                            There we have it - maybe 6mm Nosler is what it should be Someone get Bend on the line. Just use a Grendel case head please. But I have to confident that whoever designed the head on the 22 Nosler is currently bagging groceries at Food 4 Less.....

                            A 105 RDF with a G7 of .280 going faster than a 90 gr SMK at 2700 out of a 24" with a G7 of .256. Absolutely blows 224 Valkyrie out of the water with both ballistics and delivered energy. And ifthe case could accommodate a little more powder .....

                            K_4c, what sort of load are you using for the RDFs and what is your COAL/jump? I have a 26" McGowan on order and I'm getting all drooly again. The RDFs are the first thing I'm going to try.
                            8208 and h4895, 27.5-28.5 grains at mag length. With a 26" tube I bet you touch 2750 FPS. That's make for nice ballistics. Could also try a slower powder too (RL15).

                            Comment

                            • bj139
                              Chieftain
                              • Mar 2017
                              • 1968

                              #15
                              Originally posted by StoneHendge View Post
                              There we have it - maybe 6mm Nosler is what it should be
                              Is 6mm Nosler a thing?

                              Sounds good to me.

                              Did I just stonehenge this?

                              Comment

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