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Flat top upper on older AR15?

Discussion in 'Rifle Discussion' started by Dinged, May 11, 2012.

  1. Dinged

    Dinged Portland, OR Active Member

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    Hello folks, I have an older Colt AR15, 20" barrel, non removable carry handle, A2 stock. My question is, can I simply buy a flat top upper receiver assembly and put it in? How hard would that be? Could I keep my charging handle and BCG? My goal is to eliminate the carry handle and be able to mount optics on it without having to mount it on top of the handle. Is it hard to install?

    I was looking at something like this: Upper Receiver Assembly - Flat Top
     
  2. stmcelroy

    stmcelroy Madras, OR Well-Known Member

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    Sure can. It's not that hard to do but you may need to buy a few tools to accomplish it. You need a barrel nut wrench and a block to hold the upper so that it is not broken or crushed.
     
  3. eldbillbo

    eldbillbo clackamas New world samurai and a redneck none the less Bronze Supporter

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    actually depending on how old your rifle is . if you have the larger front take down pin then you will need a offset pin it a take down pin that allows you to use small pin uppers with large pin lowers they cost less than $10

    or you may want to consider this

    https://danieldefense.com/big-hole-upper-receiver-assembly-b.html

    but as stmcelroy said some basic ar15 tool and the barrel swop is a piece of cake. Plenty of guys here to help guide you through it or just utube it.
     
  4. madcratebuilder

    madcratebuilder Ardenwald, OR Well-Known Member

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    Pay attention to the pivot pin diameter. It should be a easy swap.

    I would get a upper with BCG. It's nice the keep BCG and barrels matched and together.

    If you want to keep cost as low as possible you could just buy a upper receiver and swap your current barrel, BCG and other parts. Used A3 uppers can be found for $100 or less.
     
  5. Dinged

    Dinged Portland, OR Active Member

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    Thanks guys, I ended up deciding to build another, smaller AR. Are there any tool kits you guys recommend? I'm fairly handy with tools but I've never assembled an AR before, I imagine it can't be -too- difficult
     
  6. CleverName

    CleverName Southern Oregon Active Member

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    If he has a fixed front sight tower, he would also need to change it to an F marked tower in order for iron sights to work, correct?
     
  7. DoubleTapDrew

    DoubleTapDrew Oregon Well-Known Member

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    Yes if he wants to use a mil spec rear iron sight. The standard height FSB will usually work but you'll need to raise the front sight post up above the protective ears making it more susceptible to damage.
     
  8. Skang

    Skang WA Well-Known Member

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    Just buy the decent complete upper. :thumbup:
     
  9. madcratebuilder

    madcratebuilder Ardenwald, OR Well-Known Member

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    Just depends on how anal retentive you are. As you can see there is a whopping .040' difference in the height if the FSB.

    front-sight-bases.jpg

    Most people just use this to correct the .040". I many cases you can just adjust the front post up.

    front-sight-posts.jpg