Interior Coating for Completed 80% AR Lower

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  • 2nd=Good+Substantial

    Ultimate Member
    Mar 17, 2012
    1,622
    The Hereford Zone
    I searched but couldn't find what I was looking for.

    Once the anodized 80% lower is completed, do you put a finish on the bare aluminum? If so, do you paint the pin and selector holes or does the coating make the holes too small?

    What is a good DIY coating (e.g. DuraCoat, AlumaHyde)?

    Thanks!
     

    teratos

    My hair is amazing
    MDS Supporter
    Patriot Picket
    Jan 22, 2009
    59,775
    Bel Air
    I searched but couldn't find what I was looking for.

    Once the anodized 80% lower is completed, do you put a finish on the bare aluminum? If so, do you paint the pin and selector holes or does the coating make the holes too small?

    What is a good DIY coating (e.g. DuraCoat, AlumaHyde)?

    Thanks!

    There is no need, as the FCG pocket really gets no wear. I have run into problems with the hammer/trigger pins fitting well. I just use anti-walk pins (sorry, Lord Chad) or pins with retention screws.
     

    Batt816

    Ultimate Member
    MDS Supporter
    Dec 1, 2018
    4,087
    Eastern Shore
    There is no need, as the FCG pocket really gets no wear. I have run into problems with the hammer/trigger pins fitting well. I just use anti-walk pins (sorry, Lord Chad) or pins with retention screws.

    I have never heard of “anti-walk” pins, but I need a set for one of my polymer80s....... thanks.
     

    Mule

    Just Mule
    MDS Supporter
    Sep 14, 2013
    652
    I have never heard of “anti-walk” pins, but I need a set for one of my polymer80s....... thanks.

    KNS Precision makes them

    https://www.knsprecisioninc.com/product-category/ar15parts/non-rotating-trigger-hammer-pin-sets/

    As Teratos stated, if you take a SOTAR class, you'll likely hear the reasons why they aren't recommended.

    However, as with anything, there can be use cases for them. As long as you know the benefits and disadvantages, you can decide whether or not they'll work for you.
     

    trickg

    Guns 'n Drums
    MDS Supporter
    Jul 22, 2008
    14,590
    Glen Burnie
    If you don't do something with the bare aluminum, won't it corrode a bit?
    Aluminum quickly develops a thin layer of oxidation that prevents further corrosion - it's not like steel. IMO it's not something to worry about, but I am FAR from an expert on this subject.
     

    teratos

    My hair is amazing
    MDS Supporter
    Patriot Picket
    Jan 22, 2009
    59,775
    Bel Air
    Aluminum quickly develops a thin layer of oxidation that prevents further corrosion - it's not like steel. IMO it's not something to worry about, but I am FAR from an expert on this subject.

    Agree.
     

    DutchV

    Ultimate Member
    Jul 8, 2012
    4,702
    Any decent paint would be fine. The factory would anodize it, but Type III (hard) anodizing is not something most of us can accomplish at home.
     

    travistheone

    Usual Suspect
    Dec 11, 2008
    5,600
    cockeysville
    there is very little concern about corrosion damaging the metal. like someone said about it will be a surface layer and nothing more. especially if you spill a little lube down there.
     

    randomuser

    Ultimate Member
    Nov 12, 2018
    5,774
    Baltimore County

    Seagrave1963

    Still learnin'
    MDS Supporter
    Feb 6, 2011
    10,001
    Eastern Shore
    OP - I've had the same question and was kind of going to go the route of using the Birchwood Casey Aluminum black. Now, I am wondering if just leaving it alone is best. What do the rest of y'all think?
     

    Decoy

    Ultimate Member
    MDS Supporter
    Mar 2, 2007
    4,926
    Dystopia
    "BROWNELLS - ALUMA-HYDE" works pretty well but I have to agree with what others have posted, if you just leave it unfinished, it will be fine.

    I'm also a fan of the KNS pins.
     

    Bertfish

    Throw bread on me
    Mar 13, 2013
    17,606
    White Marsh, MD
    Only real bad combo would be bare aluminum contacting stainless steel. I don't even think stainless pins are available and if so there's absolutely no purpose.
     

    Mule

    Just Mule
    MDS Supporter
    Sep 14, 2013
    652
    What are the reason against the non rotating pins?

    Here's a writeup that Chad had posted, previously, which describes the reasoning in detail, and far more eloquently than I could hope to, despite my class notes.

    If i remember correctly, I believe it had been posted here on MDS, first, but currently lives on the SOTAR Facebook page, as well as Forward Controls' website.

    https://m.facebook.com/SchooloftheAmericanRifle/posts/1938889129737315

    https://www.forwardcontrolsdesign.com/anti-walkanti-rotation-pins.html
     

    cstone

    Active Member
    Dec 12, 2018
    842
    Baltimore, MD
    I just finished up a batch of 80% lowers in the white. I plan to leave one raw, one in Rustoleum, one Alumahyde, one Cerakote, and will come up with something for the others as I need them and based on the resulting wear of the above finishes. I also plan to use anti-walk pins in a few of the lowers and not in others, just to see how long it takes to egg a pin hole (my hypothesis is no damage in my lifetime). I don't plan on putting any type of coating on the insides of any of the lowers except for any accidental over spray.

    Based on the Cav Arms polymer lower I use for my 5.45 AR, I don't expect significant wear on any of these non-anodized aluminium lowers. The major stress point on a lower is the threaded portion where the buffer tube is attached. After that, it is rotating hammer and trigger pins and some detent pins and springs. Not having any coating at all makes it very easy to thread some of the smaller holes and just use set screws to retain the detents and springs.

    I don't think I saved any money using 80% lowers, even if I discount my time. I like not having any roll marks on them. I may eventually have one engraved and type 3 anodized, but in no hurry to do so.
     

    RetiredArmyGuy

    Active Member
    Jan 16, 2018
    171
    Pasadena, MD
    I have lowers that are probably 10 to 15 years old that have never been finished on the inside and they are fine.

    When you start coating the inside of a lower you may find you run into tolerance issues depending on the type of finish and the coating depth.

    I used to DuraCoat everything inside and out but now I just leave internal areas alone.
     

    Bertfish

    Throw bread on me
    Mar 13, 2013
    17,606
    White Marsh, MD
    I don't think I saved any money using 80% lowers, even if I discount my time. I like not having any roll marks on them. I may eventually have one engraved and type 3 anodized, but in no hurry to do so.

    You won't save a dime doing them as 80s. I keep looking at the 80% glocks but it ends up being more than a factory Glock. The 1911s seem to end up about the same for an 80 and a good quality factory gun.
     

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