A shop I worked in stopped taking in the 1916 Spanish Mausers that were converted to Nato cal. Both in trade and for repairs.
Liability reasons and from what I saw I'd say for good reason.
Most had excess headspace. Some had their bolt lugs peened back a bit to take up the slack. Bubba jobs for sure, but the bolts certainly should not have been that soft to be able to peen the metal on the lugs in any direction.
I never had the 7.62 bbl off of one to see the locking lugs in the recv'r, but I suspect they had been set back on the xcess HS specimens.
Some you could feel the bolt drop into the set back area when they are really bad. On test firing, the action would be extremely hard to open. That goes for any BA rifle.
The NATO round as well as the 308 Win is just a touch too much for that action and era of mfg.
The orig design of the pre-98 was for a line of cartridges that at that time produced a service pressure in the area of 42K psi.
The OTC Nato rd and the 308 commercial rds sold today can be loaded to 60 & 62K psi.
That's a 50% increase in service pressure over what the orig 7mmx57 was at the time of mfg for these 1916 Mod 93 Mausers.
That's a Proof Load.
Can they take it?,,it seems as so,,they hang together w/o becoming a fragmentation bomb. At least no one admits to any such event that I'm aware of.
The rifle is supposed to be able to take a Proof Load. But not a steady diet of them.
Most all of these Spanish mfgr 1916 Mod 93's were made in the 20's and 30's.
Ask most anyone and they won't own any Spanish made firearm from that or most any other era. Junk,,soft metal.
10cents on a dollar,,they might buy something and even then it's a hard maybe.
But these,,,these were cheap surplus and together w/cheap Nato ammo at the time made happy buyers.
One in good mechanical condition in this cal with proper reloads in the lesser psi range would do fine.
But to push the upper+ limits of the action w/ commercial ammo doesn't seem in the best interest of your face and hands. Even more so if the action and bolt is improperly heat treated..
Even if still in 7x57,,most all of the commercial OTC ammo in that cal sold today is loaded to the low 50K psi level to satify the modern rifles made in the caliber.
That is already over what the orig 1893 Mausers were made for.
These are 100 yr + old service rifles w/ unkn historys and arsenal conversions that may or may not be of the best quality & QC.
Examine carefully and then if shootable, take it easy on them.