I'm sure you're right about the casting. It's just that when I look at this receiver and all of its contours; both inside and outside, it's hard for me to picture exactly how they'd go about milling such a receiver. If anything, it must have taken many, many additional post-machining steps and alot of hands-on work to get it to its finished stage. The "Die Forging" mentioned by the good Cap'n Morgan might very well be the way they went about it. I'd never heard of that till just now.
I suspect the cam surfaces in the receiver started out flat just like on most conventional rifle receivers. The Swiss must have come up with some type of jig to grind them to the desired angles.
I do own a small Grizzly 4003-Gunsmithing lathe and a small Tormach 770 CNC mill with a forth-axis feature. Photos of this same machinery can be seen on the internet by just googling them. What I don't have is enough free-time to play around with these toys as I'd originally hoped when I took possession of them.
I dream of being able to retire some day and playing around with these machines to my hearts content.
HollowPoint