I know you want a tight upper to barrel connection, but is there too tight?

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  • bob4432
    Warrior
    • May 2016
    • 175

    I know you want a tight upper to barrel connection, but is there too tight?

    I have a few spares laying around and one that I picked up is a BCM 'blem' and it is so tight I can't even get the barrel extension started. I added heat like they say with a hair dryer, to no avail. A friend recommended putting it in the oven @ 400F, but I am worried if it did fit, what would that do to the Loctite? I knew when I bought it that BCM said on their site that their uppers were tighter than others, but if I can't even get the extension started, well, how do I start?

    Any tips on holding the upper to get it started would be appreciated and also what about the 400F oven, or even a 200F oven trip. My buddy figured putting the whole upper in the oven would allow the entire upper to expand, and not just parts like you would get with a heat gun.

    I must say, I am wondering if this one is just too tight or is it a gem by being so tight?

    Thanks in advance for any assistance,
    Bob
  • Hoser1
    Bloodstained
    • May 2015
    • 71

    #2
    When I put my AA side charger and JP barrel together, I used a dead blow hammer to get mine seated. It did start into the upper okay, then got gradually tighter as it was being seated. Have you put a micrometer to see what the difference is? you stated that it was a "Blem", is it possible that all the machining wasn't complete? Maybe "truing the upper" might be enough to get it to seat. Hopefully some more experienced guns builders will chime in. Get yourself an upper holding block, that will help in your build, not only to seat the barrel but to get the barrel nut torqued.

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    • rabiddawg
      Chieftain
      • Feb 2013
      • 1664

      #3
      Put the barrel in the freezer over night then put the upper in the oven. If it slides in you should be good until you need to separate them again. Separating them will surely be a b tch but you will definitely have that tight fit.
      Knowing everthing isnt as important as knowing where to find it.

      Mark Twain

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

      Comment

      • NugginFutz
        Chieftain
        • Aug 2013
        • 2622

        #4
        As rabiddwawg says, barrel in the freezer and upper in the oven. A fit this tight does not need any loctite bedding. Doing so, in my opinion, is consigning your knuckles to a future bruising, if you ever decide to separate the two.
        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

          #5
          These are the best fits when you get them like that. Follow the advice above. I would put it in the oven. You won't need any adhesive for this mating.
          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

          • bob4432
            Warrior
            • May 2016
            • 175

            #6
            Thanks for the responses. Will do what you guys recommend. Being new to building I will do a couple 5.56 uppers first in looser uppers, then pick up a cheap toaster oven to heat it up in, putting a gun part into my wife's oven would bring the wrong "O" face , also currently finding deals in case things do not go our way here in a couple months
            Last edited by bob4432; 06-08-2016, 01:07 PM. Reason: Phone auto correct got me :(

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