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tCan 06-25-2013 03:22 AM

Casting a receiver - lost foam
 
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.

c3shooter 06-25-2013 03:56 AM

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.

tCan 06-25-2013 07:08 AM

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.

SSGN_Doc 06-25-2013 02:28 PM

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.

MrTrizzae 06-25-2013 09:51 PM

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.

Axxe55 06-25-2013 10:07 PM

Quote:

Originally Posted by tCan (Post 1286159)
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.

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.

HankStone 06-25-2013 10:14 PM

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

gunnut07 06-27-2013 01:27 AM

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.

hiwall 06-27-2013 03:05 AM

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).

tCan 06-27-2013 04:42 PM

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.


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