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FAL 80% build

Discussion in 'Gunsmithing and Repairs' started by John_Doe, Feb 7, 2019.

  1. John_Doe

    John_Doe Member

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    I picked up a 80% fal receiver at a gun show for $15 and figured this would be a fun project to do in my spare time. I kinda would like to talk to somone who has actually done this before so if you have I would be very thankful for any help you can provide.
     
  2. MachIVshooter

    MachIVshooter Member

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    They're pretty involved, gonna need a decent amount of tooling.

    Before you even consider building it out, make sure it's a quality part. There were more than a few junky castings put out
     
    troy fairweather likes this.
  3. Kabic

    Kabic Member

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    FAL FILES forum is where you need to start reading
     
  4. John_Doe

    John_Doe Member

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    I have a mill and i can buy end mills the use , and how would i know if mine is a bad casting?
     
  5. BBBBill

    BBBBill Member

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    Magnaflux is one way. Any info on who cast it? Maybe some online research.
     
  6. Sebastian

    Sebastian Member

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    Nice avatar.;)
     
  7. BBBBill

    BBBBill Member

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    I will second the FAL Files Forum. Also, it is best if you can find a set of blueprints for the receiver. Everything on a gun is machined based on a datum line/lines. That reference point is critical to getting everything properly located. Without blueprints to establish the correct reference points you chances of success are slim. Without blueprints you will not even be able to tell if the casting is large enough in all the right places to finish machine to spec. Example - the 1911 pistol datum is the center of the slide stop pin hole. Everything locates from that point. I have seen 1911 castings that were scant material in some spots rendering them unusable if finish machined.
     
  8. John_Doe

    John_Doe Member

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    It was cast by century arms , and whats magna flux?
     
  9. John_Doe

    John_Doe Member

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    I found some blue prints online so i think i got that covered
     
  10. John_Doe

    John_Doe Member

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    Thanks bro
     
  11. BBBBill

    BBBBill Member

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    Magnaflux is done by machine shops on engine blocks and other items to find microscopic cracks and voids in an item. They often can X ray an item to see voids, too.
     
  12. Bwana John

    Bwana John Member

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    How you gonna heat treat it (without distortion) after machining?
     
  13. Sebastian

    Sebastian Member

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    Magnafluxing is a type of magnetic particle inspection. You use a handheld, "magnet gun" (AC magnetic yoke) and a colored magnetic powder. You would place a magnetic arm from the yoke on either side of a suspected crack and them magnetize the area and lightly puff the magnetic powder onto the area in between the magnets. If there is a crack it will magnetically adhere into the crack and make it very obvious.

    magneticyoke.jpeg

    For non-magnetic materials you would use a DPI/LPI (dye penetrant inspection) process.
     
  14. John_Doe

    John_Doe Member

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    Well im not sure but what are the dangers of a improper heat?
     
  15. John_Doe

    John_Doe Member

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    Ohhhhhh a weld check i went to weld school and i forgot the name, they use it to check for internal cracks and porosity right?
     
  16. boom boom
    • Contributing Member

    boom boom Contributing Member

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    I'm not a FAL guy but regarding improper heat treatment of a receiver,
    The item can be warped which on a semi auto makes it difficult to function reliably (see things like rewelded military receivers, etc.) , made brittle (strong like glass but can shatter or crack), or be too soft which means wear is accelerated (won't stand up to recoil). Heat treatment is best left to to professionals with precise controls but for them to successfully do their work--they need to know the composition of the receiver as different alloys require different temperatures etc.

    However, my guess is that you have an aftermarket investment cast receiver block rather than a raw forging. Depending on the material used, it may or may not need heat treatment or only need it on specified surfaces. As I said, I am not a FAL guy so I do not know how much stress from operation is placed on specific areas of those receivers.

    That being said, your first task is to find out who made the casting/forging which was probably made for the relatively few companies that assembled FAL's or sold receivers for them when they became available. Ideally, there should be some identifying marks that can be used on the receiver so that someone familiar with those receivers could identify it and explain more fully the issues involved in turning it into a working receiver. I would suggest online forums that specialize in the FAL in the DIY sub sections (http://www.falfiles.com/forums/index.php for example ) might be able to shed more light on the receiver blank that you have. They might also be able to identify jigs, templates, etc. that can help you finish the receiver so that it is safe and reliable in operation.
     
  17. John_Doe

    John_Doe Member

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    Ok man i will look into all of that, my parts are coming in so far all i can do is refinish the wood , thanks for all your help i kinda suspected how the heat treat might affect the receiver so far it sounds like i might want to go on the soft end and not have the locking shoulder brake and fly into my face, I've been talking to my uncle about this and hes giving me a lot of good machining advice. Thanks for the advice
     
    boom boom likes this.
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