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.