rough chamber neck

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  • Rickc
    Warrior
    • Aug 2016
    • 311

    rough chamber neck

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    Last edited by Rickc; 09-23-2016, 01:30 PM.
  • NugginFutz
    Chieftain
    • Aug 2013
    • 2622

    #2
    The marks in your bore appear too far down the tube to be causing the scratches that long on the case neck. From the pictures of the case, it looks more like the barrel extension / feed ramps.

    I have heard those marks referred to as "vampire" marks, and are usually cause by sharp edges on the feed ramps. Polishing with a Dremel tool with a soft, semi-abrasive tip with a fair measure of patience should do the trick.

    More on that here:
    I have read that some people like to polish their feed ramps..... Can anyone elaborate on just how exactly this is done? Do they also polish the portion of the feed ramp that is on the upper receiver? How does that affect the hard coating on the aluminum upper? Just want to be sure I get this right... So much to learn.
    If it's true that we are here to help others, then what exactly are the others here for?

    Comment

    • A5BLASTER
      Chieftain
      • Mar 2015
      • 6192

      #3
      Do you have a adjustable gas block on this barrel.

      If so check placement to insure proper line up and open the block a few more rounds.

      My JP barrel did the exact same thing when I shot it the first time, the bcg locked up and I had to take the rifle apart to clear it and my brass looked just like the pic you posted.

      I put it back together opened the gas block more and bang everything worked properly, I then was able to adjust the block for perfect operation.

      Not saying this is your problem but wont hurt to check before you go to putting power tools into the chamber of your barrel.

      Also whos barrel are you useing the horde would like to know for future knowledge.

      Comment

      • cory
        Chieftain
        • Jun 2012
        • 2985

        #4
        Having a BCG lock up is not uncommon when you fire a barrel for the first time. I've gotten to the point I'll fire at least 10+ rds before trying to manually trying to cycle the bcg after the first firing. I don't know if this actually fixed the problem or the other barrels didn't have the problem, but I haven't had the problem since. The barrels work perfectly afterwards.

        The first time I experience it was with a .223 wylde barrel I got from PF. I thought I was going to have to take a mallet to the charging handle when I finally got it to cycle. After putting a mag through the barrel I haven't had any other "problem" and she shoots lights out now.
        "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

        Comment

        • LRRPF52
          Super Moderator
          • Sep 2014
          • 8569

          #5
          Those marks on the neck are normal for AR15s. They happen when the spent case is extracted and the ejector is putting off-axis force on it, causing it to slam against the lead edge corners of the barrel extension teeth after the mouth clears the chamber.

          You need to diagnose why you had failure to extract in the first place.

          What gas system length do you have?

          How did you install the gas block?
          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

          Comment

          • ricsmall
            Warrior
            • Sep 2014
            • 987

            #6
            I agree with 52, those marks are from locking lug recesses in barrel extension. Last two barrels I put together were tight like that on first few shots. One of them was cut with a minimum spec saami reamer and factory amax was jamming. I put my Manson saami reamer in there and it only went in 3/4 of the way before stopping. I reamed it out and it's fine now. The chamber was in spec, just minimum spec.

            The other one was a jp and the gas block needed to be opened a bit more for proper function. Long story short, I wouldn't be putting flex hones in a top tier barrel of any caliber. Those tool marks look to me like they're in the rifling, but that may be just me looking at the pics. Hope this helps

            Richard
            Member since 2011, data lost in last hack attack

            Comment

            • Rickc
              Warrior
              • Aug 2016
              • 311

              #7
              Well I thought I would do a little update on my rough chamber neck thread.

              Work has been hell lately. Had to take over a project that was a.month behind schedule. 24/7 and the owner is moving.in Monday. Needless to say I haven't gone to the gun range lately

              I did get the flexhone and polished up the chamber. Went to the gun range this morning and she functioned flawlessly. I even turned the gas off and you could easily cycle the action with the charging handle.

              Started with 30 gr. of cfe223. Put 10 rounds down range checking function and playing with the gas block. Very pleased. I wasn't even trying for accuracy but those 10 shots were all within an inch and 5 were touching.

              Shot 5 5 shot groups with charges from 30 to 31.2 gr. 30 and 30.3 were the best. Lots more load development to come. Take my crony next time. Seating depth test and might try the 8208 XBR.

              Now this is an 18" lightweight I built for hogs and coyotes. Never intended it to be a precision rifle. Got plenty of them. They are too heavy to carry.

              You guys were right abouto one thing. Those two scratches are on every piece of fired brass along with the usual dented case mouth. AR's are rough on brass.

              Comment

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