First time to the range with new build. What gives?

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  • Crabra
    Unwashed
    • Aug 2017
    • 19

    First time to the range with new build. What gives?

    So this is my first AR build built almost entirely from scratch...

    36774417576_a41c66c0a9_k (3).jpg36134064464_8a9f46a243_z.jpg

    I took it back and a different guy at the shop said the same thing about the alignment. It also had an excessive amount of gas on the ejection port. More to follow guys, just wondering if these guys are on the money with their assessment?

    Also, do I need an adjustable gas block? Mine is the .750 so I thought that was sufficient.
  • Crabra
    Unwashed
    • Aug 2017
    • 19

    #2
    Additionally I looked at my BCG purchase and it is a AR stoner...not sure if this is the problem or the barrel?
    Last edited by Crabra; 09-02-2017, 02:40 PM.

    Comment

    • rabiddawg
      Chieftain
      • Feb 2013
      • 1664

      #3
      The problem with the ammo pictured is caused when the bolt doesn't travel far enough to the rear to pick up the round at the base of the case. Which would lead me to believe the system is under gassed. What happens is friction of the bolt coming forward causes the round to move forward until it hit the feed ramps where the tip of the bullet begins to move up until the bolt wedges itself into the case body.

      I had one that ran fine for a couple hundred rounds then started intermittently doing that. Long story short I noticed a bit of leakage around the gas block. I replaced the gas block and it has run fine ever since.

      Excessive gas around the ejection port could mean you have a leak somewhere which would be the same effect as under gassed.

      We won't be able to help with your "chamber alignment" issue without pics.
      Last edited by rabiddawg; 09-02-2017, 12:48 PM.
      Knowing everthing isnt as important as knowing where to find it.

      Mark Twain

      http://www.65grendel.com/forum/showt...2-Yd-Whitetail

      Comment

      • Crabra
        Unwashed
        • Aug 2017
        • 19

        #4
        I appreciate that rabiddawg, so I'm going to have them take a look. I forgot the brand of the gas block I paid for, might just be installed incorrectly...

        Comment

        • rabiddawg
          Chieftain
          • Feb 2013
          • 1664

          #5
          I have Avery scientific way I check them.

          Plug the changer with a rag. You should be able to blow thru it with a little resistance.
          Knowing everthing isnt as important as knowing where to find it.

          Mark Twain

          http://www.65grendel.com/forum/showt...2-Yd-Whitetail

          Comment

          • Crabra
            Unwashed
            • Aug 2017
            • 19

            #6
            So is this a possibility...the magazine was hitting the table or digging into the table while I was zeroing? In any case I'm taking her to the range tomorrow to see how it goes...and I'll be raising the bipod legs

            Comment

            • Crabra
              Unwashed
              • Aug 2017
              • 19

              #7
              Day two at the range...about 40rds in and the same problem occurs. Click no boom, bolt has rode forward onto the round bit the round at the bottom only. I have video as well. It's not the best but you can see the malfunction.

              Comment

              • Crabra
                Unwashed
                • Aug 2017
                • 19

                #8
                I haven't tried the rag method yet

                Comment

                • Crabra
                  Unwashed
                  • Aug 2017
                  • 19

                  #9
                  IMG_0213.JPG

                  Comment

                  • DJL2
                    Bloodstained
                    • Aug 2017
                    • 57

                    #10
                    That's a lot of mangled brass...
                    Looking at the feed ramps on your barrel, they match fine with your lower receiver. I suppose it's possible that the barrel and chamber could somehow be so far out of alignment that even with the barrel extension and feed ramps matching there's an issue...

                    However, I am inclined to agree with rabid - that looks like your BCG is short stroking. I'm just not used to seeing brass get quite that mangled. Does the action cycle by hand? Does it feed and eject without issues when you "sling shot" the charging handle all the way to the rear? If it feeds by hand, it ought to feed on its own without issue - unless, of course, it's not getting the gas it needs. Again, I suppose it's possible you could get a upper receiver and BCG that are so far out of spec they're not running on "normal" gas - but, the gas port size, gas block alignment or some combination is a more likely issue.

                    For reference, I had a 6.8 SPC barrel where someone goofed on gas port size and I had to drill it out. It would short stroke, need to be mortared, have ridiculous problems...but, I don't remember it doing the brass quite that badly...though 6.8 brass is a slightly different animal, of course.

                    Comment

                    • Crabra
                      Unwashed
                      • Aug 2017
                      • 19

                      #11
                      Check out the video guys:

                      As far as I can tell it is simple to use the action. The round simply gets shoved in at a bad angle and prevents the BCG from closing. I can easily retract the bolt drop mag and drop the round. 24sec mark I let the 1st rd fly then JAM.



                      I fucking cuss on that vid...just in case you have virgin ears

                      What are my options here? I have minimal weapons experience. Can a gunsmith check those BCG and Barrel tolerances? And what can I do to fix this gas port?

                      Comment

                      • maxxmojo
                        Bloodstained
                        • Jul 2016
                        • 99

                        #12
                        Have you tried a different mag, or tried it without a mag in it?

                        Comment

                        • Crabra
                          Unwashed
                          • Aug 2017
                          • 19

                          #13
                          Originally posted by maxxmojo View Post
                          Have you tried a different mag, or tried it without a mag in it?
                          That is actually the next step. I've been using ASC mags and it seems to be scraping the round on the way out. I ordered a Alexander arms 5rd and will be test firing soon

                          Comment

                          • DJL2
                            Bloodstained
                            • Aug 2017
                            • 57

                            #14
                            There are a few places you can download specifications for the AR-15. To reiterate, the likelihood of the BCG/upper being the issue is much less than the magazine or the gas system being the issue. You can check parts dimensions yourself with a good set of calipers and a micrometer. However, the AR is designed to have "room" around the gas key and the bolt carrier in general - if you look at traditional BCG wear you usually see it in just a few places - specifically, the flats. You can get some machinists die (forget the actual name...you know, the blue stuff that shows parts interference), degrease your upper, paint it and run it a few times to see where it's wearing if you're concerned. You'll also see some wear on the bolt lugs/face, of course.

                            When you run the bolt by hand it should feel...hmm...how to put it...a bit like 1200 grit sand paper on a smooth piece of wood. Just a hint of friction, but a nice, easy back and forth glide with next to no effort (other than pulling against the action/buffer spring). If that's the case, your BCG should be behaving pretty normally. They can feel a touch "gritty" when new. It looks like you're running a round into the chamber without problems, too. I can tell from your photos you're not trying to run the rifle dry, so that shouldn't be the issue.

                            Based on your photos and the video, the rounds are "beaching" themselves on the feed ramps. That means either your magazine is FUBAR, you're under gassed or...well...lets just leave it with those two for now.

                            As far as the gas port goes, I am new to the Grendel game...you and I would both need to look up the proper port diameter for a 16" tube with a...which length gas system did you say? Carbine? Mid? If you find a smith make sure they have experience with the 6.5 specifically. The other thing is, I didn't see how your gas block is installed. The industry easy button for this is a gas block that is located and fixed with 2+ set screws. If the fit around the barrel is "loose," some green loctite can help. It appears that's what Sanders uses...but, again, I'm not sure on your specific setup.

                            You can measure both the barrel and the gas block to ensure that your reference features on the gas block and barrel correctly position the gas block over the gas port. I am assuming the gas tube is correctly installed. If everything lines up and the parts are properly installed, you've eliminated most all potential problems here.

                            If this all sounds complex...well...I suppose it is a bit. Try the magazine thing first - that is by FAR the easiest potential fix. I'd check that for sure before I started getting into checking the gas system and potentially drilling out the port.
                            Last edited by DJL2; 09-04-2017, 01:10 PM.

                            Comment

                            • Crabra
                              Unwashed
                              • Aug 2017
                              • 19

                              #15
                              Thanks a lot guys, DJL2, it is two set screws for the gas block so I'll be checking that after the magazines. I have a carbine length.

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