You have to machine 2 places on the receiver to make it auto
That's not the case on the Carbine.
The sole and only difference between a MARKED M2 Carbine and an M1 marked Carbine is the number "2" or the number "1".
The receivers are precisely the same.
The auto parts are in the trigger group and operating slide assembly.
That's what makes all this so stupid. The receivers are the same other than that small number, and the number alone makes it a machine gun.