I worked on one of these in 2006. Was a semi auto AR-10 looking contraption that Dakota Arms was contracted to build for Cheyenne Tactical. I left before it was finished, but I hear it didn't go so well.
Anyways, Mark Jameson, owner of Jameson international in Sturgis, SD manufactures brass. least he used to back then anyways.
Be prepared to invest significant time and money getting the components put together so that they'll function. The brass will all need to be full length resized and carefully prepared.
I'll leave it at that.
Bear in mind that nothing is cheap with this hog.
Nothing. . .