AR build issue

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  • slickshot223
    Unwashed
    • Apr 2017
    • 19

    AR build issue

    Ok, here we go, a friend has brought me his 6.5 Grendel that he can't seem to get shooting any better than 1 1/2 at 100 yrds!! The loads that are posted on some of the forums, along suggested loads from the manuals, with accuracy of 3/4 inch or less will absolutely not shoot in this rifle!! The barrel is a Stoner 1-8 twist 5R 18 inch SS. The assembly seems to be in good shape!! Have ask him to bring me some of the same loads he has been trying to see if I shoot any differently!! Results seem to be the same!( ya I know that doesn't mean much!!LOL) The fired brass has carbon residue on every fired case about half way back the brass! Compounded by FTF of one in 5-6 rounds fired!! With the carbon on the brass and the FTF one would think that the chamber pressure was lacking, but the loads used are all at the higher end of the suggested loads! The heads space checks as it should!!
    Now for some of the findings. When cleaning the barrel I find a loose area about an inch ahead of the gas block opening, the patch becomes loose as it passes that area then tightens again, then about the last inch and a half of the barrel the patch becomes much tighter than the rest of the barrel making one think the barrel is choked!
    Thoughts: the loose area maybe contributing to the carbon issue due to chamber pressure drop, as the gas fills the loose area, and may also contribute to the FTF issue!! The choking of the last portion of the barrel may be effecting the accuracy!!
    YOUR THOUGHTS????
  • Steamburn
    Warrior
    • Apr 2015
    • 133

    #2
    Get a new barrel from the seller.

    Comment

    • VASCAR2
      Chieftain
      • Mar 2011
      • 6218

      #3
      A lot of the 18" Stoner barrels have large gas ports which contibutes to the system being over gassed. Many owners have used an adjustable gas block to alleviate the over gassed system. Over gassed and under gassed will sometimes perform the same. The one bullet that seems to give consistent accuracy out of the Satern/Stoner Grendel II chamber are 120 grain Sierra Match Kings.

      If you know someone with a bore scope it would be worth looking at the inside of the barrel. If the barrel has been bedded in the upper receiver and torqued to spec with a proven scope and mount. Then have a good shooter try but if it still won't shoot the 120 grain SMK I'd call Midway. The Stoner barrels are rack grade and the odds are just as good you get an average to poor shooter as a very accurate barrel, basically luck of the draw.

      Comment

      • StoneHendge
        Chieftain
        • May 2016
        • 2009

        #4
        Has he tried Hornady factory ammo? Whenever I build a new rifle, I always start with factory ammo to rule out that any problems could be from my ammo (except if you build a 458 Socom, don't test it with Black Butterfly - that stuff is junk)

        My 18" Stoner shoots factory 123 Amax at 5/8". It took forever to find a hand load - so much so that I almost gave up on it. Turns out my barrel is fast and my loads are much below what others use here. Was just ringing steel with it at 750 2 hours ago in a 15 mph wind.

        Also sounds like your friend hasn't been doing ladders with his loads......... And using higher charge loads? I wouldn't put some of the loads I see on the world wide web in my chamber without wearing a crash test dummy suit.
        Last edited by StoneHendge; 06-15-2017, 10:56 PM.
        Let's go Brandon!

        Comment

        • slickshot223
          Unwashed
          • Apr 2017
          • 19

          #5
          It doesn't shoot factory loads either!! I agree with the web loads, I usually look at those for information only, then go to the loading manuals to correlate what might be a decent load!!
          And yes he has been using the ladder approach to find a good load!!
          I don't consider myself a bad shooter, was out this afternoon with 2 gas gun and a bolt action shooting bugeye groups!! 100 Yds!!
          Am about to suggest to him it's time for a different barrel!!
          Thanks for the help guys!!

          Comment

          • just_john
            Chieftain
            • Sep 2012
            • 1565

            #6
            You did not include any target pix. Is there a sense of pattern to the holes - vertical or horizontal stringing? To repeat Vascar's question, was the barrel bedded? It has been my experience ( and repeated by many others across this forum ) that unless the mated barrel to upper required a cryo treatment then bedding is in order. Without it, there IS barrel movement within the upper which will randomize POI. Presumes that all bolts are otherwise tight.

            Comment

            • jcjarmon
              Bloodstained
              • Dec 2016
              • 69

              #7
              First problem I see is the 5r barrel. Barrels with 5 rifling groves are fine in bolt guns. But not in gas operated ARs. When you bore the gas port, the hole lands in one of the 4 rifling. On a 5r barrel, that's not really doable. I bet whoever sold you that barrel, ether didn't know what they were talking about, or had the same problem your having, and just wanted to get rid of it. Thats why you'll never see a Krieger 5R Ar-15 barrel. There's no such thing.

              Comment

              • mdram
                Warrior
                • Sep 2016
                • 941

                #8
                Originally posted by jcjarmon View Post
                First problem I see is the 5r barrel. Barrels with 5 rifling groves are fine in bolt guns. But not in gas operated ARs. When you bore the gas port, the hole lands in one of the 4 rifling. On a 5r barrel, that's not really doable. I bet whoever sold you that barrel, ether didn't know what they were talking about, or had the same problem your having, and just wanted to get rid of it. Thats why you'll never see a Krieger 5R Ar-15 barrel. There's no such thing.
                many companies make 5r for the ar platform, includin bartlein
                nothing wrong with 5r
                just some targets for printing
                https://drive.google.com/drive/folde...xQ?usp=sharing

                Comment

                • slickshot223
                  Unwashed
                  • Apr 2017
                  • 19

                  #9
                  Originally posted by just_john View Post
                  You did not include any target pix. Is there a sense of pattern to the holes - vertical or horizontal stringing? To repeat Vascar's question, was the barrel bedded? It has been my experience ( and repeated by many others across this forum ) that unless the mated barrel to upper required a cryo treatment then bedding is in order. Without it, there IS barrel movement within the upper which will randomize POI. Presumes that all bolts are otherwise tight.
                  Target are sometimes random and wide spread then other times large but symmetrical!! The barrel has been loctited to the receiver!

                  Comment

                  • slickshot223
                    Unwashed
                    • Apr 2017
                    • 19

                    #10
                    After reading issues on another post it would appear that the BCG is getting too much gas!! Plus one of the post here suggests that Stoner barrels have too large gas ports! Will give this a look as soon as I find out what port size is correct for an 18" barrel!! I do know that the buffer is a 5.2 oz, took it to the PO today had it weighed!!

                    Comment

                    • StoneHendge
                      Chieftain
                      • May 2016
                      • 2009

                      #11
                      Originally posted by slickshot223 View Post
                      Target are sometimes random and wide spread then other times large but symmetrical!! The barrel has been loctited to the receiver!
                      Is the muzzle brake firmly attached and is it the "helioplex?"
                      Let's go Brandon!

                      Comment

                      • slickshot223
                        Unwashed
                        • Apr 2017
                        • 19

                        #12
                        Originally posted by StoneHendge View Post
                        Is the muzzle brake firmly attached and is it the "helioplex?"
                        No muzzle brake!! crown looks good, however am going to have it freshened after I address the gas port issue!

                        Comment

                        • Klem
                          Chieftain
                          • Aug 2013
                          • 3506

                          #13
                          I hate to say it but you get what you pay for.

                          Don't ignore the obvious, it's a cheap barrel from a cheap manufacturer. 1.5MOA with factory ammo from a Stoner barrel sounds normal. You might get lucky and score the occasional good one but that's why you'd be lucky, because most people don't. The accuracy you expect costs twice as much from a handful of manufacturers who make Olympic-grade barrels.

                          Comment

                          • Retro
                            Warrior
                            • Jul 2016
                            • 150

                            #14
                            Can someone tell me what a helioplex is? I Googled the word and all that I get are things about suntan lotion and skin care products.
                            Originally posted by StoneHendge View Post
                            Is the muzzle brake firmly attached and is it the "helioplex?"

                            Comment

                            • StoneHendge
                              Chieftain
                              • May 2016
                              • 2009

                              #15
                              Originally posted by Retro View Post
                              Can someone tell me what a helioplex is? I Googled the word and all that I get are things about suntan lotion and skin care products.
                              Satern's muzzle device - it's on the rifle in this thread
                              Finally got my FDE Grendel into her natural environs and remembered to take some pictures while the barrel was cooling. Aero Precision lower and COP upper. Current scope is a Vortex Viper 2.5x10. Been wanting to go to higher magnification and was contemplating the Bushnell LRTS in FDE over the winter - until Midway started
                              Let's go Brandon!

                              Comment

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