OK, here are a couple of other things to look for. Is the barrel an original German made barrel? If it is, it will have a serial number with an acceptance mark above it. The mark is a circle within a circle with 4 equal spaced marks between the 2 circles. Most of the serial numbers do not match the receivers. The back of the receiver will be stamped "7.62 N" with the N under the number. The receiver and the barrel were blued whereas the original receivers were in the white. I can see the insert in mine by looking at the extractor slot cut in the receiver, the insert is not the same color as the receiver and a faint line is visible. If yours does not have these characteristics, someone may have installed a new barrel not of Chilean origin, however I do not know of any other 29" military barrels that were original 7.62. It would have to be an after market barrel. To get a 7.62 chamber in a 7x57 Mauser barrel, you just about have to use an insert because the 7,62 case is so much shorter than the 7x57.
You can shoot the commercial loads in the re-chambered rifles and not expect an immediate problem, but there is probably going to be erosion with time and a higher pressure load will accelerate this. There is a web sight by "Dutchman" ( goggle "Chilean chamber insert" and it comes up first) that shows the erosion of the soldered joint with time and explains the difference between nato and commercial ammo.