The Chilean Mausers I have seen in 7.62 NATO were converted by reboring and rerifling the original barrel, then drilling out the back of the barrel and inserting a new chamber. I don't know if that conversion was done by the Chileans to upgrade rifles that would be used only in an emergency or was done by the importers. Either way, it might be safe enough, but I would not care to trust it to 60k pressures.
Check the picture; yours is probably the same way.
Jim
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