Type 1/2 Problem

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  • Smitters
    Unwashed
    • Aug 2017
    • 20

    Type 1/2 Problem

  • CastorTroy
    Warrior
    • Mar 2015
    • 133

    #2
    you need to stick with whatever bolt the barrel was chambered with. however, i doubt that the bolt face is what is causing your accuracy issues. can you share your load info?

    Comment

    • Dcommoncents
      Warrior
      • Jul 2017
      • 164

      #3
      There are some really good threads sticky'd at the top of this section that address the bolt/chamber differences much more competently than I can hope to. In short though, you're right that you would need to have the chamber modified to headspace with a 0.136" bolt, which probably wouldn't make sense given the relative abundance of reasonably priced barrels currently available on the market. I also don't see any reason why the 0.125" bolt would cause your handload accuracy issues, but don't know enough to intelligently comment further so I'll leave that to the gurus who lurk here.

      Comment

      • grayfox
        Chieftain
        • Jan 2017
        • 4295

        #4
        I doubt seriously if the barrel can be re-chambered. If I understand the dimensioning correctly, the 0.125 bolt face-style chamber is already 0.011 too deeply cut into the barrel to be able to accept a 0.136. If you don't want to stick with that barrel you'll need to get another that is set to accept 0.136 depth bolts. Check the stickies on the grendel chamber as described above.

        There are, as Dcc stated, many good, well-priced barrels out there. Depending on how Model1 assembled its upper you may be able to use the other pieces/parts.. Or get a different, completely-assembled upper with the appropriate barrel.
        "Down the floor, out the door, Go Brandon Go!!!!!"

        Comment

        • VASCAR2
          Chieftain
          • Mar 2011
          • 6219

          #5
          Smitters it’s always been my understanding Model 1 Sales used 6.5 Grendel .136 bolt face with their 6.5 Sporter barrels. It’s entirely possible the original buyer was using the wrong bolt. A rifle barrel that was chambered to use a .136 bolt would probably function with a .125 bolt but would have excessive headspace. Looking at Model 1 Sales web site they list a BCG for there 6.5 Sporter. Model 1 Sales also list 7.62X39 BCG. I think if I were you I’d call Modell 1 Sales to see if they have ever chambered their 6.5 Sporter to use a .125 bolt. It would be good to know if M1S has used both bolts like Black Hole Weaponry who coined the Type I designation for .125 X39 bolts and Type II for .136 6.5 Grendel bolts.

          If the barrel was chambered to use a .136 bolt I’d probably buy a Group buy 6.5 Grendel bolt from the forum. It would be a good idea to measure your supplied 7.62X39 bolt to see if the length is 2.81 and uses a milspec firing pin. Some 7.62X39 firing pins are enhanced with a longer tip to ignite hard military primers on steel cased 7.62X39.

          Take a look at this thread there are pictures with the milspec AR-15/M-16 firing pin and 2.81” bolts.


          Last edited by VASCAR2; 12-05-2017, 11:15 PM.

          Comment

          • Kswhitetails
            Chieftain
            • Oct 2016
            • 1914

            #6
            Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

            Comment

            • Smitters
              Unwashed
              • Aug 2017
              • 20

              #7

              Comment

              • Dcommoncents
                Warrior
                • Jul 2017
                • 164

                #8
                Originally posted by Smitters View Post
                You guys are awesome! I mean really awesome, any other forum I’m a member of would have absolutely chastised me for having a momentary brain fart and missing the stickies. I get so used to scrolling past them I don’t even read them anymore. I hate to get rid of my 6.5 grendel because this forum is such a wealth of actually useable information and it’s delivered with professionalism and usually lacks the dramatics of other forums. I think a call will be made tomorrow in hopes they can educate me further.
                Agreed, as a relative new-comer I was struck by the same outstanding forum culture here. I do my best to maintain and contribute to that.

                Comment

                • Clarence
                  Bloodstained
                  • Dec 2015
                  • 53

                  #9
                  A question for VASCAR and others: If the chamber was reamed for a 0.136" bolt and the OP is using a 0.125" bolt, it would take factory ammo at least 0.011" short on headspace for the rifle to function. Is the factory ammo that short?

                  If that is the case, the FL sizing die would likely not set back the shoulder. THE OP didn't elaborate on his reloading problems. If this is it, he could find it quickly by measuring the shoulder location with a Hornady (or other) tool.

                  Clarence

                  Clarence

                  Comment

                  • VASCAR2
                    Chieftain
                    • Mar 2011
                    • 6219

                    #10
                    Clarence: I think I miss spoke in my post in regards to whether the barrel was chambered with a .136 bolt and them used a .125 bolt. A .125 bolt would reduce the available room and may not chamber a round. If the round did chamber the bullet could be stuck in the lands significantly raising pressure. If unsure which bolt the barrel was chambered it’s best to consult the manufacture or use a set of go,no go gauges.

                    If the barrel was chambered using a .125 bolt and you switched to a .136 bolt +.001 or -.001 you have more additional room and could have excessive head space. Excessive head space would tend to blow out the shoulder, probably shortening the life of the brass and might eventually lead to a case head seperation. Ultimately just know which bolt your barrel was chambered to use!

                    The problem arises that certain manufactures/vendors have deviated from the norm and chambered barrels with .125 bolt face depth X39 bolts. The consumer needs to do a little research when buying any variant chamber for the AR-15 as there can be certain pitfalls. I think it’s even worse if you delve into the large frame AR-10 7.62/6.5 CM/260.

                    Ultimately just know which specific bolt your barrel was chambered. It’s not a bad idea to have a spare bolt and an extra extractor as the extractors are not inter changeable. The 6.5 Grendel bolt takes a 6.5 Grendel extractor.
                    Last edited by VASCAR2; 12-06-2017, 03:38 PM.

                    Comment

                    • NugginFutz
                      Chieftain
                      • Aug 2013
                      • 2622

                      #11
                      +1 on carrying spare bolt. Better yet, an entire BCG (which I do for two different calibers). Complete gas key, firing pin and bolt remedy in one easy-to-install package. This allows me to get back to the fun stuff quickly, and troubleshoot at leisure.
                      If it's true that we are here to help others, then what exactly are the others here for?

                      Comment

                      • LRRPF52
                        Super Moderator
                        • Sep 2014
                        • 8569

                        #12
                        I thought Model 1 Sales used after market bolts.

                        They break frequently in 5.56, so I personally don't ever buy anything from them.

                        A lot of the broken bolts in the after market were Model 1 Sales and "6.5 Sporter".
                        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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