Guess again - stamped & bent... The bending jigs you can get online are usually copies of Russian patterns.
Misha Kalashnikov spec'd stamped/bent steel receivers because it was cheap, it was easy, and it vastly reduced the number of operations (and therefore opportunity for error.) A couple of stampings would shape it and punch the holes, a trip to the press would fold it to shape - and assemble.
Like I said, the OLD ones were milled. They didn't become stamped until the AKM. Guess again, indeed. Lol
By the way, his name was Mikhail, not Misha. I think one of his kids was named Misha though IIRC. It don't matter though, I prefer a Simonov over a Kalashnikov anyway.
Craftsman hand tools are drop forged if I'm not mistaken.