The good news is that [url]www.mr40mm.com[/url] sells 80% machined minigun receviers and some misc parts like bbls.
The bad news is (according to gun industry gossip) is that Mike Dillon is a badass. He bought every piece of tooling and parts for the minigun from GE. He's the only guy that can make the things work reliably. He doesnt bid on contracts, the .gov comes to him. What that means basically is that there are no competitors for the business which means that Dillon isthe only one who makes new parts.
Now, that doesnt mean there isnt any old parts lying around out there somewhere. Youll have to do ALOT of digging and researching for them, but you might find them.
Also, the patent for the minigun ran out long ago, I think, and since Dillon isthe only the .gov buys from, theres no need for a patent.
To sum things up, I'd start at Mr40mm and see if he can help you. Hope I was somewhat helpful