So I was at the gym last night, got on the treadmill, flicked on the tele and Sons of Guns was on.
Question: If you build an AR upper reciever to which the magazine attaches directly does that change the definition of the type of reciever, require serialization, FFL transfer, etc...?
They had a .50 caliber upper attached to an AR lower and got around the magazine well size limitation by just hanging the larger magazine to the left of the upper reciever like some enormous Sten gun (but bolt action). I was thinking that removal of that much support material right behind the chamber might not be a great idea for a big bore rifle but don't mind me.
Disclaimer: I don't own either an AR or a .50 caliber anything. I'm just curious.