AR15.Com Archives
 Can I buy casting molds for 80% recievers?
Kalahnikid  [Team Member]
11/5/2007 8:42:31 PM EST
I registered for a welding and aluminum casting class for my final semester of college next spring. I know I will have access to the Alum casting equipment as part of the class, so can I buy a mold to make receivers?
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ILove2Shoot  [Industry Partner]
11/5/2007 9:53:53 PM EST
I am sure if you want to have a mold made you can, just have to cough up the dough. The mold will produce what is refered to as a forging or casting. these are not in a 80% state....the magwells are usually one solid piece of metal and also the area where the buffer tube goes into is solid........I have no idea how much a mold would cost for this, but my guess is a couple grand on the cheap side. not, you could always just make your own sand mold for a one time pour.
Kalahnikid  [Team Member]
11/5/2007 10:44:48 PM EST

Originally Posted By ILove2Shoot:
I am sure if you want to have a mold made you can, just have to cough up the dough. The mold will produce what is refered to as a forging or casting. these are not in a 80% state....the magwells are usually one solid piece of metal and also the area where the buffer tube goes into is solid........I have no idea how much a mold would cost for this, but my guess is a couple grand on the cheap side. not, you could always just make your own sand mold for a one time pour.


Hmm, I was hoping I could buy/rent a hard steel mold that would allow me to cast a few 80%'s
PromptCritical  [Team Member]
11/5/2007 10:56:10 PM EST
Buy one casting and use it to make the sand castings.

From one, many.
mercedesman  [Member]
11/6/2007 2:22:13 AM EST
You can't make a casting from another cast part, or any finished part for that matter. If you remember metal shrinks in size as it cools, and aluminum shrinks A LOT.
Any parts you make need to start from an oversize mould or core. You'll learn that in class....
JimM44  [Member]
11/6/2007 4:26:26 AM EST
Couldn't you make a lost wax mold from an 80% lower?
ILove2Shoot  [Industry Partner]
11/6/2007 7:14:03 AM EST

Originally Posted By JimM44:
Couldn't you make a lost wax mold from an 80% lower?


no, wont work. considering the metal shrinkage, if you poor into a mold that starts as the exact size needed it will be to small when finished because the alum will shrink when cooling. also, if you need to do some surface finishing with a mill, wont be to easy to do inside the mag well. also sand molds have a left and right side (or top and bottom), and since the magwell and the back of the receiver where the buffer tube goes are at 90 degrees of each other, you will have one of them as a solid chunk.

just dug up this link to give you a good idea of what is involved and what you will end up with.....

link to 0% and 80% information
akubli  [Team Member]
11/6/2007 7:38:42 AM EST
Double tap
akubli  [Team Member]
11/6/2007 7:38:52 AM EST
For a pattern you can take a casting and build it up with some kind of slip material to make up for the shrinkage. In Aluminum it is in between 2 and 3% if I remember correctly. Then you just ram up your sand mold and cast it like normal. It would be a pretty simple cope and drag mold when you are done. Hmm... makes me wander about using a core to get the magwell in it also. I need a 0% for my next casting project. Thanks for the idea, I had never thought of mixing my 2 favorite hobbies till now(metal melting and guns)
mnd  [Team Member]
11/6/2007 7:51:36 AM EST
You've got a 1/4" per foot of shrinkage.

Take a stripped lower and some thin wax. Dip the lower in the wax several times to build up a coating to account for shrinkage. You'll probably have to add some draft by hand when you're done.

Take another stripped lower and use it to form plaster cores for the magwell, FCG cutout, and trigger area.
Trim these cores so they'll fit in the waxed lower.

You could probably use undersized steel pins for cores for a few of the holes in the receiver.

Take pictures.

Let us know how it works out.
Kalahnikid  [Team Member]
11/6/2007 7:58:02 AM EST
I know nothing about metal casting (partly why I taking a class about it, duh) but I have done some bullet casting and I was hoping that I could buy a reciever mold that I could fill with molten alumnium to make a reciever (like casting a bullet)

I was really just curious if such activity was possible. Ill probably drap this thread back up with more questions when I get intot he class in January. Thanks to those who answred my questions!
mnd  [Team Member]
11/6/2007 8:05:24 AM EST

Originally Posted By Kalahnikid:
I know nothing about metal casting (partly why I taking a class about it, duh) but I have done some bullet casting and I was hoping that I could buy a reciever mold that I could fill with molten alumnium to make a reciever (like casting a bullet)

That would actually be pretty slick. A mold for a DIY 95% lead receiver.

Though actually if you used it to cast wax positives and used those to make a plaster negative that you cooked the wax out of I bet you'd get pretty good detail and finish.
PromptCritical  [Team Member]
11/6/2007 9:25:50 AM EST

Originally Posted By ILove2Shoot:

Originally Posted By JimM44:
Couldn't you make a lost wax mold from an 80% lower?


no, wont work. considering the metal shrinkage, if you poor into a mold that starts as the exact size needed it will be to small when finished because the alum will shrink when cooling. also, if you need to do some surface finishing with a mill, wont be to easy to do inside the mag well. also sand molds have a left and right side (or top and bottom), and since the magwell and the back of the receiver where the buffer tube goes are at 90 degrees of each other, you will have one of them as a solid chunk.

just dug up this link to give you a good idea of what is involved and what you will end up with.....

link to 0% and 80% information


Did not know that. Never came up in my high school metal shop class. Then again, we never even thought about casting any precision parts either.
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