Howard these are the "flats" he's referring to . No they're not flat that's just the terminology,
and your correct that such a "flat" would be hard to recreate those at home
View attachment 72519 View attachment 72520
View attachment 72521 a completed receiver
View attachment 72522 a bending die kit to bend the "flats" into their final shape
I've built FALs , but I've never built a 91 although I have looked into "building" a receiver,
I'd have to do a lot more research before I'd attempt it , welding it up would be the least of my worries. that's easy .
Getting the "flat" bent in the proper way [the 1st time] to function correctly is what I'd be worried about.
All those dies look like a PITA