An MAS is not worth the troubke of milling a receiver for one. Check armslkst, they pop up on there from time to time. The only way id go to milling a receiver for a gun is if it was a k43 or something lol.
"Is that you John Wayne? Is this me?"
"You can go a long way with a smile, but you can go a lot further with a smile, and a gun."