6.8 SPC bolt from 223/5.56 bolt

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  • bj139
    Chieftain
    • Mar 2017
    • 1968

    6.8 SPC bolt from 223/5.56 bolt

    Does anyone have any idea if a 223 bolt can be opened up slightly in a small lathe to function with a 6.8 SPC case?
  • Tex Nomex
    Warrior
    • Dec 2017
    • 185

    #2
    Originally posted by bj139 View Post
    Does anyone have any idea if a 223 bolt can be opened up slightly in a small lathe to function with a 6.8 SPC case?
    Don't try it. You'll just ruin the bolt and extractor.
    The bolt and extractor would need to be thinned in their thinnest areas and the face depth looks to be different. Just find a cheap 6.8 somewhere.
    "The best we can hope for concerning the people at large is that they be properly armed."
    -- Alexander Hamilton, The Federalist Papers at 184-188

    Comment

    • NugginFutz
      Chieftain
      • Aug 2013
      • 2622

      #3
      Fpni
      If it's true that we are here to help others, then what exactly are the others here for?

      Comment

      • bj139
        Chieftain
        • Mar 2017
        • 1968

        #4
        Now I've got to try it.

        I was asking if anyone knew about doing it not that it should not be done.

        The naysayers will always say it should not be done.

        Comment

        • Tex Nomex
          Warrior
          • Dec 2017
          • 185

          #5
          Sorry 'bout that unwanted advice I gave earlier. I guess I didn't read your post closely enough.
          Good luck. Video please.
          "The best we can hope for concerning the people at large is that they be properly armed."
          -- Alexander Hamilton, The Federalist Papers at 184-188

          Comment

          • NugginFutz
            Chieftain
            • Aug 2013
            • 2622

            #6
            One of the overarching concerns would be the removal of surface hardened material. These bolts are heat treated, and grinding / milling / cutting will only compromise the surfaces in one of the areas where hardness is most needed.

            Is it really worth the cost of a new bolt to see if you can do this? I'm not familiar with your machinist skills, bj139, but even if you are successful in hogging out the bolt face, are you certain you want a compromised bolt?

            ETA:

            If you're really convinced this is something you want to try, at least follow the lead of people's opinions you might better respect.

            Has anyone opened up the face on a AR15 bolt to PPC size. ( .445 ) I would just buy an 7.62x39 bolt but they seem to be in short supply righ now, at least the three suppiers I use. Looking at the .223 bolt face and an 7.62x39 bolt face, it looks like they just open up the face, I'm just...
            Last edited by NugginFutz; 01-14-2018, 07:45 PM. Reason: <IYF>
            If it's true that we are here to help others, then what exactly are the others here for?

            Comment

            • Randy99CL
              Warrior
              • Oct 2017
              • 562

              #7
              Originally posted by bj139 View Post
              Now I've got to try it.

              I was asking if anyone knew about doing it not that it should not be done.

              The naysayers will always say it should not be done.
              Hey, I'm on your side! You can't know whether someone advising you knows more about it than you do.
              Make sure you make a video when you fire the gun for the first time.
              "In any war, political or battlefield; truth is the first casualty."

              Trump has never had a wife he didn't cheat on.

              Comment

              • bj139
                Chieftain
                • Mar 2017
                • 1968

                #8
                NF,
                Practical machinist was one of the sites that said any good smith could open up the bolt.

                I would not try this with the Grendel because too much material must be removed (0.032") but with the SPC only 0.022" must be removed.

                I bought 2 group buy Grendel bolts so I have 2 extra 223 bolts just gathering dust.
                Last edited by bj139; 01-14-2018, 11:26 PM. Reason: Spelling

                Comment

                • StoneHendge
                  Chieftain
                  • May 2016
                  • 2009

                  #9
                  It's your face and you can do whatever you want with it, but please be conscious of anyone who might be sharing the range with you
                  Let's go Brandon!

                  Comment

                  • bj139
                    Chieftain
                    • Mar 2017
                    • 1968

                    #10
                    IMG_20170802_132336 (Medium).jpg

                    I'm getting some mileage out of this photo. I posted it another thread yesterday.

                    Comment

                    • Tex Nomex
                      Warrior
                      • Dec 2017
                      • 185

                      #11
                      From my experiences with 2 6.8 SPC ARs, even when running boxed SSA ammo with an adjustable gas block, the 6.8 SPC is pretty hard on every part of a bolt.

                      I have an early 'snowflake bolt' that would be somewhat comparable to what you're suggesting. It's face stretched to 11mm in fewer than 1000 rds and I started having extraction issues.

                      I've run superbolts or something similar since then. Strangely, right now I have a 9 yr-old snowflake bolt in a 16" 6.8 RRA after wearing out the lugs on an ARP bolt (Top in the photo below). Not going to buy another until I see how my new Grendel build performs. Might re-barrel the RRA for 65Grendel or another 223...

                      Those side walls are gonna be mighty thin if you carve them out...

                      The worn snowflake bolt below (middle) has a 1.37mm wall at its thinnest point adjacent to the bolt face.

                      3Bolts:
                      Top: ARP Superbolt
                      Middle: Snowflake
                      Bottom (black): new 223
                      3Bolts (Medium).jpg

                      Not saying it can't be done. Just saying build a 300BLK pistol instead.
                      "The best we can hope for concerning the people at large is that they be properly armed."
                      -- Alexander Hamilton, The Federalist Papers at 184-188

                      Comment

                      • bj139
                        Chieftain
                        • Mar 2017
                        • 1968

                        #12
                        That middle bolt looks awfully thin. Are you sure thats not a 6.5 Grendel bolt?
                        Here is a photo from a site selling SPC bolts of an SPC bolt. They are out of stock.
                        SAA_PH_Bolt_68_s__66157.1489091630.jpg

                        Comment

                        • Tex Nomex
                          Warrior
                          • Dec 2017
                          • 185

                          #13
                          Originally posted by bj139 View Post
                          That middle bolt looks awfully thin. Are you sure thats not a 6.5 Grendel bolt?
                          Here is a photo from a site selling SPC bolts of an SPC bolt. They are out of stock.
                          [ATTACH=CONFIG]10791[/ATTACH]
                          Those bolts in the photo are mine. Middle is definitely a worn-out 6.8 SPC bolt from 2009-2010 back when SPC bolts were basically just milled out 223 bolts... The face on that particular bolt got pushed in and the sides worn from use.

                          The takeaway is "what will the sidewall thickness be when a standard 223 bolt is drilled out and how will it hold up?"

                          Modern SPC bolts now have a greater outer wall circumference so the walls can be thicker - similar to the ARP bolt up top.

                          "...SPC bolts of an SPC bolt?" (?) Not following...
                          "The best we can hope for concerning the people at large is that they be properly armed."
                          -- Alexander Hamilton, The Federalist Papers at 184-188

                          Comment

                          • bj139
                            Chieftain
                            • Mar 2017
                            • 1968

                            #14
                            How about this, "Here is a photo of an SPC bolt from a site selling SPC bolts."



                            I may just buy this below. Notice how much thicker the bolt web is than yours.

                            Last edited by bj139; 01-15-2018, 12:44 AM.

                            Comment

                            • Tex Nomex
                              Warrior
                              • Dec 2017
                              • 185

                              #15
                              Originally posted by bj139 View Post
                              Here is a photo of an SPC bolt from a site selling SPC bolts.
                              Makes sense when I read it now. Sorry. Brain fart on my part.
                              "The best we can hope for concerning the people at large is that they be properly armed."
                              -- Alexander Hamilton, The Federalist Papers at 184-188

                              Comment

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