12" Handguard Research for SBR Barrels

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  • BluntForceTrauma
    Administrator
    • Feb 2011
    • 3897

    12" Handguard Research for SBR Barrels

    Looking around the handguard industry, I'm seeing 12-inch handguards are sort of a standard category.

    And by 12", I mean from the front of the receiver face to the end of the handguard. There is actually a lot of variation in how these manufacturers calculate their sizes.

    My goal here is to spec a 6.5 Grendel SBR barrel where the muzzle thread shoulder starts just beyond where a 12" handguard ends, so that none of the muzzle device is inconveniently under the handguard.

    This will give us the very shortest 65G SBR barrel that still works with commonly available 12" handguards, provided the handguards are calculated in a common sense manner from the front of the receiver face, or top rail, to the end of the handguard rail.

    Going from parts drawings (and confirmed by actual measurements), AR receiver barrel threads extend 0.441" from the receiver face. Add to that the thickness of the barrel extension collar or flange of 0.131. Totals 0.572. A 12" handguard less 0.572 is 11.428. This is what the measurement on a barrel needs to be from the barrel's barrel extension shoulder to the muzzle thread shoulder.

    Muzzle thread section measures 0.625 and barrel extension thread section measures 0.620. Add to these the 11.428 and you get 12.673. Let's round up and call it 12.7".

    Three questions:

    1) Is 12" a common size you guys want to use with SBRs?

    2) Are my analysis and measurements correct?

    3) Anybody interested in 6.5 Grendel Faxon 12.7" SBR barrels specifically dimensioned to mate with common 12" handguards?
    :: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets

    :: I Drank the Water :: Revelation 21:6 ::
  • Kswhitetails
    Chieftain
    • Oct 2016
    • 1914

    #2
    This is a fun study. And difficult because there is no real standard for handguard length. How each manufacturer measures their own seems to be quite different. Some how, the length of a handguard seems to be more of a general length than an actual measurement.

    Some manufacturers seem to be using the length measurement as more of a "class" wherein because the handguard is 11.5xx but less than 12.xx we'll just put it in the 12 "class".

    Your measurements look solid. My means were much more crude, but seem to line up with your numbers from what I've seen. I would have loved to have gotten a 12.5-12.7 barrel. This would have worked perfectly with the Radical 12 or the Larue 11 that I bought, neither of which worked and I wound up having to go down to the 9 inch in order to mount the suppressor. I am still deciding if this is good enough, or if the extra inch in the 10 inch jobs is worth the time and effort to track one down.

    I could have one cut down to fit, but that would wind up wonky, and even though my pistol build is wonky at heart, I have a hard time doing this to a good piece of gear just to force it to fit.
    Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

    Comment

    • Bigs28
      Chieftain
      • Feb 2016
      • 1786

      #3
      I know several people interested in a 14.5". I think the 12" is perfect
      Last edited by Bigs28; 01-06-2018, 11:16 PM.

      Comment

      • biodsl
        Chieftain
        • Aug 2011
        • 1714

        #4
        I'm waiting for the 14.7" GB barrel

        [QUOTE=Kswhitetails;178832]Some manufacturers seem to be using the length measurement as more of a "class" wherein because the handguard is 11.5xx but less than 12.xx we'll just put it in the 12 "class".[QUOTE]

        I just measured the only "12" inch handguard I own, a MI SS Gen II. It's 12.625 inches. As a point of reference, my 13" from ALG Defense is 13" on the nose.
        Paul Peloquin

        Did government credibility die of Covid or with Covid?

        Comment

        • StoneHendge
          Chieftain
          • May 2016
          • 2009

          #5
          Originally posted by biodsl View Post

          I just measured the only "12" inch handguard I own, a MI SS Gen II. It's 12.625 inches. As a point of reference, my 13" from ALG Defense is 13" on the nose.
          Let's go Brandon!

          Comment

          • biodsl
            Chieftain
            • Aug 2011
            • 1714

            #6
            Originally posted by StoneHendge View Post
            Which means that a 12.7” barrel would be perfect under it with a Kak flashcan
            Exactly. BTF's math seems sound!
            Paul Peloquin

            Did government credibility die of Covid or with Covid?

            Comment

            • Dcommoncents
              Warrior
              • Jul 2017
              • 164

              #7
              If the plan is to use a flashcan with a 12" handguard I think you'd actually want a shorter barrel since you wouldn't need to have the crown extend to or beyond the handguard as with a traditional brake/comp/flashhider. I ran into this with the 12" faxon group buy build I just finished. I used a 12" handguard and a muzzle device very similar to a kak flashcan, except it also has a krink style brake that threads in. The device measures roughly 3.2" and as you can see extends about 2" past the 12" handguard. 20180107_085328.jpg

              So instead of a longer barrel to fit under a 12" handguard, I would actually want a shorter barrel in the range of 10.5"-11" for use with a shrouded muzzle device that can go under the handguard. While I was going for shorter, another way to look at it that a 12.8" barrel and a pinned 3.2" muzzle device would put one at 16" and out of sbr/pistol land.

              Comment

              • dpete
                Warrior
                • May 2016
                • 222

                #8
                If/when another 12" group buy barrel comes around I have a 15" carbon handguard thats going to get cut down to about 13 1/2". That way about 2" of flash can will be sticking out in front of the handguard, much like the suppressor on my 300 Blackout SBR does now. The Blackout and Grendel uppers will share the SBR painted lower.

                IMG_3018.JPG

                IMG_3017.JPG

                Comment

                • BluntForceTrauma
                  Administrator
                  • Feb 2011
                  • 3897

                  #9
                  Pete, second photo would be more interesting if it actually had a rifle in it.
                  :: 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

                  • BluntForceTrauma
                    Administrator
                    • Feb 2011
                    • 3897

                    #10
                    So am I hearing that there's too many handguard variables out there that it's pointless to try and target one size with a barrel?
                    :: 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

                    • Dcommoncents
                      Warrior
                      • Jul 2017
                      • 164

                      #11
                      Originally posted by BluntForceTrauma View Post
                      So am I hearing that there's too many handguard variables out there that it's pointless to try and target one size with a barrel?
                      Don't place too much weight on my observations, as I doubt I'll be jumping in on another short barrel group buy, but perhaps we're looking at this the wrong way. It seems to me that the variability in handguards, not barrels, is the problem. For example, I wanted to use my enhanced aero upper and handguard for my 12" faxon build. However, it is a 15" handguard, which I would have readily cut down the couple extra inches, but the way it's milled (i.e. the way the mlok slots line up with and overlap the decorative/cooling slots) it would have been impossible to get a clean, square, and structurally sound muzzle end without cutting something like 6 inches off.

                      Therefore, if none exist already, there may be justifiable interest in a group buy of handguards that are designed in such a way as to allow members to cut them with relative ease in regular increments, like the length of an mlok slot. My 12" handguard pictured above already comes very close to allowing that since the holes under the top rail frequently line up with the mlok slots. Don't know if thats feasible from a manufacturer or member interest perspective, but there are my 2 cents as to how to best solve the handguard dilemma

                      Comment

                      • Schrambo
                        Warrior
                        • Oct 2016
                        • 224

                        #12
                        So, an example of SBRs... Top barrel is a 12" Odinworks with a 11" Foxtrot HG(Measured at 10.625"), middle barrel is a 12.5" BA with the 11" Foxtrot HG. and bottom is a 11.5" Lilja with a 9" Foxtrot handguard...

                        Inconsistent lengths from barrel manufacturers make me crazy...

                        IMG_0717.jpg
                        Last edited by Schrambo; 01-08-2018, 05:29 PM.

                        Comment

                        • BluntForceTrauma
                          Administrator
                          • Feb 2011
                          • 3897

                          #13
                          Attached is a "Photo-chopped" mockup of what a 65G 12.7" barrel looks like on an Aero Precision Atlas 12" handguard (which is actually 12" from rail front to end).
                          Attached Files
                          :: 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

                          • Lastrites
                            Warrior
                            • Apr 2017
                            • 678

                            #14
                            BFT, yep that would be ideal in your mock-up. I have rails all over the spectrum, what bothers me is when a rail company doesn't explicitly state their actual length, at least Mid-Industries tells you that their 12" rail is really 12.625".

                            Comment

                            • BluntForceTrauma
                              Administrator
                              • Feb 2011
                              • 3897

                              #15
                              I really like that Midwest Industries has factory FDE options. That's what I'm looking for. Just wish they had a true 12" handguard.

                              The other one I love is the Mega Wedge Lock, but they don't offer FDE.
                              :: 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

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