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

  1. #21
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    I appreciate the info in this thread. I have a similar problem, except that the tight component in my case is the lower. I'm gonna check my take down pins and see if I have any that are smaller than the pair I was using.

  2. #22
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    If it were me, I would consider altering the take down pins (vis a vis) some real fine cloth before I would do anything to the receiver. Especially because they are known to loosen over time.



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  3. #23
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    My Vltor upper is very tight to my Noveske lower. The takedown pin really hasn't been an issue, but I couldn't get the pivot pin out w/o some type of pin punch doodad. Typically, I would use a dummy round and something to smack it with. It was equally tight going in.

    All that being said, I tried another set of pins I had lying around and it got a little better.

    Over the course of using the rifle, cleaning etc, they fit perfectly. Just a few cycles of taking the pivot pin in and out worked. Now I can push them out with just a dummy round, no smacking.

    My suggestion would be to work on the pins, not the receiver. You can always touch them up with a little cold blue if needed.
    Last edited by bp7178; 08-25-11 at 14:18.

  4. #24
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    Quote Originally Posted by rob_s View Post
    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)

    I am worried the holes are not lined up and this is causing a tight fit.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  5. #25
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    Quote Originally Posted by scottryan View Post
    I am worried the holes are not lined up and this is causing a tight fit.
    I wonder if this might be the case.
    Do you have a stripped lower to see if the holes line up correctly and if so, how much media might actually be blocking the pins from going through?
    You dig your grave with your fork.

  6. #26
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    Update.

    Tried Just the pins in the upper without the lower and while tight they were nowhere near as tight as when assembling with a lower. Put the upper on 6 different stripped lowers and the front lug for the pivot pin was too wide for ALL OF THEM. Couldn't even get it seated on the lowers far enough to get the pin in. Had to start with the upper rotated forward just to get the pin started and then closed the two halves to get the takrledown pin in. Couldn't get either pin in all the way with just my hands but in spite of pushing them in by hand had to pound them out once in.

    I ****ing hate tinkering when I'm forced to just to get a product to work right. Blow it out your ass Les Baer mothergrabber!

  7. #27
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    Quote Originally Posted by Biggy View Post
    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.
    this is what I was gong to say. pins are cheaper than receivers...
    never push a wrench...

  8. #28
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    Quote Originally Posted by rob_s View Post
    Update.

    Tried Just the pins in the upper without the lower and while tight they were nowhere near as tight as when assembling with a lower. Put the upper on 6 different stripped lowers and the front lug for the pivot pin was too wide for ALL OF THEM. Couldn't even get it seated on the lowers far enough to get the pin in. Had to start with the upper rotated forward just to get the pin started and then closed the two halves to get the takrledown pin in. Couldn't get either pin in all the way with just my hands but in spite of pushing them in by hand had to pound them out once in.

    I ****ing hate tinkering when I'm forced to just to get a product to work right. Blow it out your ass Les Baer mothergrabber!

    I'd say **** it with this upper. All you are going to do is egg out the pin holes on your nice lowers. Its either that or start sanding down the takedown lugs. Since they are oversized also.

    I know it would be nice to have a kiss upper like this with no FA and I have been thinking about a build like this myself, but I can bring myself to buy anything LB.

    I'm waiting for KAC to come out with their PDW uppers with no FA or brass deflector.

    Les Baer is a douche.
    Last edited by scottryan; 08-25-11 at 23:29.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  9. #29
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    Unfortunately this does seem like a lost cause. But since the money is spent already I may as well mess with the upper and see if I can un**** it.

  10. #30
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    If the smaller pins are a bit loose in the lower, they'll cause wear in the holes of the lower. Before lapping the holes of the upper, trim the lugs so they fit right. After getting the lugs fitted and making sure the holes of the upper line up with the holes of the lower, lap just the holes in the upper.

    The methods FTS suggested for lapping will work
    Last edited by MistWolf; 08-26-11 at 06:41.
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