Casting a receiver - lost foam

Discussion in 'DIY Projects' started by tCan, Jun 24, 2013.

  1. tCan

    tCan Active Member

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    I'm looking at casting my own receiver out of a none too specific aluminum-copper alloy for a .22LR. I intend to use what's known as a lost foam procedure. Does anyone have experience with this process or know about alloying - how to purify aluminum before alloying, etc.

    Currently, I've got about 3 pounds of computer heatsinks and several ounces of copper which I intend to alloy after cleaning the aluminum up a bit with a flux of some sort.

    Anyone who's got a good reason why this is a bad idea, speak now or forever hold your peace.
     
  2. c3shooter

    c3shooter Administrator Staff Member

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    Outside of an analytical lab, you are never going to see pure aluminum- it is alloyed with dozens of other metals to gain specific desired characteristics- in casting, machining, ductility, malleability, hardness, wear resistance, etc etc.

    Could you make a receiver out of an Al/Cu alloy? Don't know- any skills at machining that alloy? Will you have a steel barrel and chamber? What is the potential for electrolysis between Al/Cu and steel? What type of action?

    I do know that before the company was broken up/ sold off, I saw Reynolds Metals make an aluminum sub that is still in the Guiness Book of World records (Aluminaut) and they were doing a high silica alloy for piston type aircraft engines.

    Metallurgy is its own little world. I have a hard time dealing with anything more complex than O1 steel for knives.
     

  3. tCan

    tCan Active Member

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    Well, you can buy aluminum ingots... Seeing as it's a .22 I don't see how the receiver material matters much. I'm only adding the copper since it has a higher hardness than aluminum. It's a courtesy really.

    Of course I have a barrel. It would be highly illegal to have anything other than a rifled barrel. I'm building a rather crude single shot. I haven't fleshed a design out yet, I'm really just looking to find out if anyone has experience casting.
     
  4. SSGN_Doc

    SSGN_Doc Well-Known Member

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    One of the things c3 was getting at is that some metal mixtures don't play well with other metal mixtures. Iron, copper and nickel can for a bit of a electrochemical charge that can invite corrosion in the right combinations. It's not just about getting the right hardness. Brittleness, and flexibility are important as well. Sheer strength, compressability are also important, depending on repeat rubbing if moving parts, recoil compression etc.

    You can get lucky your first time making an alloy and casting it I suppose.
     
  5. MrTrizzae

    MrTrizzae New Member

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    Lost foam is.the absolute worst way to cast aluminum. Green sand is the only way to go. Take the time to make an accurate pattern and you can use it many times. The heatsinks will work great but leave the copper out. It will never alloy with the aluminum and spoil your pour. Don't forget to flux before you pour with noniodized table salt and degas with sodium carbonate. Most lowerers are aluminum anyway so the electrolysis talk will not be a problem. Aluminum has about a 2% shrinkage so you have to take that into account when making your pattern. The biggest trouble you will have is the machining of the final cast.
     
  6. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    just out of curiosity, why not just start with an aluminum bar stock? even if you cast it, it will still have to be machined in some way. might be easier to just use some aluminum stock. just an idea.
     
  7. HankStone

    HankStone New Member

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    Over my head I'd use hydraulic steel piping and machine it.
     
  8. gunnut07

    gunnut07 New Member

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    Casting is not all that strong that I have ever seen.

    I would just get some 1 or 2" Aluminum billets and go from there. If you really must machine it all yourself.

    Me really I would get a Suhl 150 restock and rebarrel.
     
  9. hiwall

    hiwall Well-Known Member

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    Obviously there are countless 22 rifles with aluminum receivers. The receiver does not really need that much strength. Your design would be a difficult part. I assume you have access to a way to melt the aluminum for the pour? Could be alot simpler to use a round receiver and just use steel or alum tubing(then you could use a round bolt).
     
  10. tCan

    tCan Active Member

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    Yes, I have a propane forge made from an old freon can and some fire bricks.

    The area which mates to the receiver is 11/16 inches in diameter, 3/4" deep. I was going to just bore 11/16 inches all the way through, make the bolt the same diameter minus a thousandth or two, notch the receiver for the bolt handle (which will also be the locking "lug") put in a simple free float firing pin in the 12 o'clock position and a simple trigger, tap for a scope, done. I'll work out a stock later.

    Not sure if I can get a proper extractor accomplished, so it might just suck a lot pulling the casings out. But I don't see why it wouldn't be safe being a single shot and all. It might spit a bit of fire with the way I'm locking it up, but that's what safety glasses are for. My Marlin 60 spits anyway....

    My goal here is to make a firearm for essentially free. I've got the aluminum and barrel already. The rest of it is going to have to come from my noggin.

    Oh, by the way. I don't even have a drill press. A chop saw, scroll saw, and a drill is all I have in the way of machining. Gonna try and find a neighbor with a press.
     
    Last edited: Jun 27, 2013
  11. JWagner

    JWagner New Member

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    Those heat sinks are usually extruded alloys, which would not be all that good for casting. There are many types of aluminum alloys that should be matched to the manufacturing process used. What I would recommend is that you use an alloy that is suitable for gravity casting processes. The easiest way to do that is to melt down some old aluminum castings that were obviously sand castings, which is most likely A356 alloy. I worked for a company that did lots of lost foam castings in the 1980's onward. The foam patterns can become distorted from pressure applied by the sand. The sand has to be tamped down by a vibration process if I recall. And not just any sand will work well. There are spherical sands and jagged sands and so on. In short, this will not be as easy as you might hope. Maybe some more web search, including Youtube is in order.
    PS: I just remembered that Saturn engine blocks were lost foam castings in their early days. That would be a good alloy to melt down.
     
  12. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    one thing i see is there is a lot of heat involved in melting down aluminum for casting. lots of potential for getting hurt if not extremely careful. are there poisonous fumes from melting aluminum? my father was an electrician with Alcoa Aluminum for many, many years in the electrical department and i know he had to carry a respirator with him every day he worked there. now melting might be different than smelting aluminum, but i would surely check into it to be on the safe side.
     
  13. tCan

    tCan Active Member

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    Aluminum vapors are certainly not something I consider pleasant.
     
  14. Crazycastor

    Crazycastor New Member

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    After you cast it are you planning on doing any maching work to it? When you cast something you have to remember that the metal will shrink meaning it won't be the same size you cast because of the cool down. Expect at least 1/16 of an inch shrinkage. If it was me I would machine your idea if you have the equipment.
     
  15. Vikingdad

    Vikingdad New Member

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    I would not even consider lost foam for casting a receiver. If anything I would machine it out of a billet.
     
  16. tCan

    tCan Active Member

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    Ah, to be rich.
     
  17. clr8ter

    clr8ter New Member

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    Believe it or not, there are some jobs that a hammer will not do. This is one of them. And if it were easy or cheap to cast receivers for guns, everybody would be doing it. I work in the metal trade, and have access to some machinery and a lot of talented people. I was thinking about machining an 80% AR lower. I decided that this was too much even for me.

    I'd say go buy a used Savage Crickett. They're not very expensive, even new.
     
  18. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    Blasphemer! how dare you say such a thing? there is nothing a hammer can't fix or build and to think otherwise, then your man card should be revoked immediately!:eek:
     
  19. clr8ter

    clr8ter New Member

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    LOL. ok ok, I'll amend to say if a hammer won't do the job, you just need a bigger hammer.....How's that?
     
  20. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    much better!;)

    heck, i can even repair my watches with a large hammer and a crowbar!:p