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Thread: Lapping an AR receiver?

  1. #11
    Quote Originally Posted by LittleLebowski View Post
    I’ll hit you up for my 5.45 sooner or later. It needs a new rail and I’ll lap it then.
    You’re still running the 5.45?! How’s it holding up?

  2. #12
    I've done it.

    I used a Brownells tool on my Sionics OEM upper. Did the following:
    -lapped the receiver
    -glued the barrel extension using green loctite
    -"floated" the gas tube

    I did a before /after comparison with a few different loads. I saw a massive improvement with some loads(ADI, Creedmoor, Hornady) and almost no change with others (IMI, Wolf Gold, PPU).

    In my sample of one the loads that shot "well" beforehand didn't change much. The match loads which shot poorly originally improved by quite a lot.

    If I were building a new upper I would do it by default.

  3. #13
    I'd be very afraid of galvanic corrosion if the anodic coating is removed from any surface that contacts steel or stainless steel.

  4. #14
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    Quote Originally Posted by mtnbkr View Post
    It doesn't touch the inside of the receiver. The portion of the tool that rotates within receiver extension where the barrel inserts is reduced in diameter. It's not quite as reduced where it sits in the bolt channel (prob wrong terms), so it doesn't cause any wear as long as you lube it well. The only place it removes anodizing or metal is where it contacts the receiver face and that's because you use lapping compound at that spot.

    Chris
    So you are really laying the receiver extension and barrel face ?

  5. #15
    If you're using/buying from a quality manufacturer I wouldn't think its necessary. That should be checked in the QC process. At least I would hope so.

  6. #16
    Quote Originally Posted by mkmckinley View Post
    You’re still running the 5.45?! How’s it holding up?
    Like a good Gun 3 Glock 9mm
    #RESIST

  7. #17
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    Quote Originally Posted by HCM View Post
    So you are really laying the receiver extension and barrel face ?
    I was sloppy in my description. It only touches/laps the upper receiver face. None of the internal (including the internal interface of the barrel extension and receiver) are affected.

    This site shows how it works.

    Chris
    Last edited by mtnbkr; 07-08-2019 at 06:42 AM.

  8. #18
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    Quote Originally Posted by Paul Blackburn View Post
    If you're using/buying from a quality manufacturer I wouldn't think its necessary. That should be checked in the QC process. At least I would hope so.
    I suppose it depends on the original specifications. I wouldn't think the original mil-spec would be that detail-oriented. To be honest, I'd only consider this useful (in a theoretical sense) for target rifles where group size and consistency are the goal.

    It appears to be a commonly accepted step for target rifles, which is why I gave it a try on my 20" build.

    Chris

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