Page 2 of 8 FirstFirst 1234 ... LastLast
Results 11 to 20 of 74

Thread: Uber-tight upper:lower fit, how to loosen?

  1. #11
    Join Date
    Mar 2011
    Posts
    187
    Feedback Score
    0
    Quote Originally Posted by Failure2Stop View Post
    I have had some very tight upper/lower fit rifles and carbines.
    I made them acceptable with the following methods:

    1- Slow. Completely strip pins and lugs of any lubrication. Using nylon punch, repeatedly insert and remove pins until do-able by hand while shaking assembled weapon.

    2- Medium. Completely strip pins and lugs of any lubrication. Rub pin hole in upper lugs with Flitz or a bore paste. Cycle pins as above.

    3- Fast. Be careful, if you make you upper looser than a Phillipino lady-boy, it ain't my fault. Be warned.
    Take a new brass bore brush and chuck it into a variable speed hand-drill. Insert brush into takedown pin hole. Start slow, gradually increasing speed of the drill. Check fit frequently.

    I would avoid drill bits and files.
    Quote Originally Posted by Thomas M-4 View Post
    Use a old take down pin load it up with lapping compound and chuck it in a drill . Never tried it just an idea.
    Yea basically what failer2stop posted along with the same precautions.
    My thinking is in parallel with the above posts.
    I might try using a set of those EZ-Pull Pins for tools along with bore paste/lapping compound combined with elbow grease (cycling).

    If elbow grease was not enough I would chuck up some bar stock of the correct diameter in a cordless with bore paste and hit it with some slow, careful RPM.
    Last edited by DirectDrive; 08-25-11 at 10:56.

  2. #12
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,121
    Feedback Score
    112 (100%)
    I would try lightly sanding the pins with some crocus cloth and leave the holes alone. Crocus cloth comes in 3 grits and is used for fine finishing of metal parts. If you have any extra takedown pins laying around check them for fit, I have had some that were .001" undersize.

  3. #13
    Join Date
    Jun 2011
    Location
    Back where I belong
    Posts
    1,661
    Feedback Score
    2 (100%)
    I guess I stand corrected. But I've yet to have dramatic overkill"ladyboy" looseness(that really is funny F2S). But I see how it could easily happen in the wrong hands.

  4. #14
    Join Date
    Jun 2006
    Location
    SE FL
    Posts
    14,148
    Feedback Score
    5 (100%)
    I'm actually pretty sure that even with power tools I wouldn't screw this up.

    This thing is INSANELY tight. I've seen tight before, but this is just bananas. I am not at all exaggerating when I say I have to beat on the pins to get them to seat, and I do mean beat.

    The one thing I haven't done yet is test-fit loose pins to the holes to see how that goes. I can tell you that unlike some tight uppers I've dealt with in the past it doesn't matter which pin you drive in first, both are equally tight, which leads me to believe that both holes will need opening up.

  5. #15
    Join Date
    Nov 2009
    Posts
    226
    Feedback Score
    36 (100%)
    I have dealt with this problem a couple of times. You don't need power tools. I have used both a small, round, fine file and and a wooden dowel with 150 grt sand paper.

    Open up both holes a little at a time, frequently rechecking fit. My best guess is you will barely remove the anodizing inside the holes before you get the fit you want.

  6. #16
    Join Date
    Nov 2010
    Location
    MI
    Posts
    3,055
    Feedback Score
    21 (100%)
    Hey Rob

    As has been said, the front pivot pin hole should be round while the takedown is elongated front to back.

    I'd work on the front first and use the shank of a 1/4" drill bit with lapping compound either by hand or chucked.
    This one should be a precision fit.

    Once that is set, move to the takedown.
    If that is round it may need to be elongated with a file.
    This hole does not need to be as pretty.
    Black River Tactical
    BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
    BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
    BRT EZTUNE Preset Gas Tubes - CAR and MID
    BRT Covert Comps 7.62, 5.56, 6X, 9mm
    BRT MarkBlue Gas Tubes - BRT EXT, EXC and PDW Lengths
    BRT MicroPin Gas Blocks - .750" & .625"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

  7. #17
    Join Date
    Feb 2009
    Location
    MA
    Posts
    1,612
    Feedback Score
    10 (100%)
    IIRC there was a thread on TOS by a guy that had the same problem with a brand new rifle he bought from them.

    He sent it back and they told him they fixed it and shipped it back to him. They ground/machined/filed the top of the lower and the guy was not happy with it.

  8. #18
    Join Date
    Jul 2006
    Location
    Oregon
    Posts
    3,459
    Feedback Score
    2 (100%)
    If it's going to be used with a specific lower I'd try smaller pins before removing metal.

  9. #19
    Join Date
    Jun 2007
    Location
    The Free State of Nebraska
    Posts
    5,427
    Feedback Score
    7 (100%)
    Are the pins in the upper tight by themselves or are they tight for the whole upper/lower assembly?

    I take it you are using one of their flattop uppers without a forward assist? Correct?

    If that is the case, another option would be to buy a Colt 750 LMG upper, remove the receiver, and sell off the rest. I know this isn't very likely but is another way to get what you want and their won't be any **** ups.
    Last edited by scottryan; 08-25-11 at 13:38.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  10. #20
    Join Date
    Jun 2006
    Location
    SE FL
    Posts
    14,148
    Feedback Score
    5 (100%)
    I need to test fit loose pins in the upper. I haven't done that. I've tried mounting the upper on every lower I have (several Colts, several BCM, an LMT, a Sully, and an old Bushmaster) and in all cases the pins have to be pounded in with a rubber mallet to get them in.

    Yes, it's a Baer flattop non-FA. I'd love to have a 750 stripped upper but something tells me that would be cost-prohibitive.

Page 2 of 8 FirstFirst 1234 ... LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •