EDIT: I don't remember using any arsenal produced CETME, so unfamiliar with how their barrels are made.
Interesting. Have used a lot of H&K (mostly G-3s and MP-5s (K, SD, etc) while in the military. Both stateside and overseas. Even used the Paki licensed stuff while working in Pakistan. But they were all original arsenal produced weapons. Believe they were all hammer forged barrels. Not sure what H&K is currently using for re-barrelling.
Tozguy: I've reloaded lots of range pick ups from civilian H&K 91s and 93s. Back in the day when brass was hard to come by locally, the fluted stuff was all the range scavengers would leave on the ground. The locals thought it was unfit for reloading.
Holes creek: Nice documentation with how you cut the fluting. How much polishing does the chambers require? Any issues with extraction?