Yep, they're made in Spain. The base mount holes are threaded for standard base screw (pitch 6-48). There could be a slight burr, or some preservative in the holes, and possibly on the screws too. Talley rings should have 6-48 pitch also, but they might be a different length overall. The Bergara barrels do not have some sort of oddball Spanish metric screw size.
I've got a couple of the barrels, but since I did clean up the mounting holes and the screw threads, they went in fine. I'd find a gunsmith if they gave me trouble like you described, because any gunsmith worthy of the name has scope mounting 6-48 taps lying around like the rest of us have screwdrivers and crescent wrenches.
Wallypedal