So, Eli, it's a European-made Mauser.
(I don't have a reference for, specifically, Chile.)
European Mausers were properly strong actions, made of good steel and correctly heat-treated.
What's it's original bore size? Was it made for a 7.62mm cartridge, or a 7.65mm?
(I suspect the latter, but I don't know. If I'm right, the extra 0.011" of bore diameter could affect accuracy, but not chamber pressure, adversely.)
If its bore is 7.62mm or very slightly larger, the next step is: "Was the chamber recut properly?"
To ascertain that, you need at least a "no-go" headspace gauge, and it would be better to also have a "go" size.
Then, you'd need to investigate the barrel's lede.
Absent the proper gauge, I suggest just barely seating a jacketed bullet into an empty, unprimed case, and slowly closing the bolt on it until you feel resistance. If the case comes out with the bullet still in it (rather than it having stuck in the rifling), you can compare it to a factory-loaded case. This will tell you just how far the bullet has to "jump," in order to catch the rifling. It should have to "jump" a small distance, certainly under 1/4", but "jump" is what it should do. It should not be right up against the rifling.
If all that checks out, you might tie the gun to an old truck tire, and use a string to pull its trigger remotely. Examine it after each shot.
If it stays intact, it's most likely OK.
(I hope that I'm not insulting you by "teaching gran'ma how to suck eggs.")