One should always realize that Gun Magazines make their profit from ads, not subscriptions. Therefore their recommendations are always tainted to please the advertiser.
The Spanish ring Mauser was built for the 7mm Mauser cartridge which operated at 3000 atmospheres pressure. All of the small ring cartridges, the 6.5 X 55, the 7 X 57 mm, and the German 8 X 57 mm service cartridge operated at 3,000 atmospheres, which is approximately 43,371 psia. By the time WW2 rolls around, the German service cartridge was 46,000 psia but no one has shown a pressure increase for the 6.5 and 7mm service cartridges.
No country builds rifles with the express desire to have them blow up in the faces of their users, and Militaries do know the structural limits of their weapons, and the good ones issue ammunition tailored to the weapon.
I am have not conducted serious research into Spanish conversions or their ammunition. But it is known that the Spanish had a less pressure version of the 7.62 Nato cartrige, the 7.62 X 51 CEMTE.
https://en.wikipedia.org/wiki/7.62×51mm_CETME
Google translated this text from this web page:
http://www.municion.org/762x51/762x51Esp.htm
https://municion.org/
Spain, isolated from the international community, continues to use 7.92x57. Beginning in 1953, prototypes of cartridges began at 7'62 x 51. In 1955 this caliber was adopted and shortly after it began to be mass produced for the new CETME. It should be noted that this cartridge does not meet NATO standards and is called 7'62x51 Spanish. In the '60s, they improve quality and are renamed 7'62x51 NATO-SPANISH. CETME assault rifles models A and B could only fire these cartridges. Used with 7.62x51 standard NATOs deteriorated rapidly. Version C solved this incompatibility, and any weapon prepared for the NATO cartridge can be used in Spanish without problems. Only since 1988 the cartridges produced in Spain are referred to as NATO-ORDINARY and meet the specifications of this body.
The velocity of the 113 grain, plastic core bullet was 2600 fps is referenced here:
https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/7.62×51mm_CETME.html
Needless to say, you don't need much pressure to push a 308 caliber 113 grain bullet to 2600 fps. Someone with a ballistic program could come up with pressure estimates.
I am going to claim that these 308 conversions were built to use the 308 CEMTE cartridge. And yet, once they reach our shores, who is exactly telling buyers not to use 65,000 psia commercial cartridges in the things?
There will always be the deniers, and I am sure one will roll around and claim "this is your opinion!!". I am of the opinion that these rifles can be reloaded for safely by keeping the pressures appropriate for the action. This is assuming no receiver seat set back, which would initially be noticeable by hard extraction, (assuming the receiver does not blow first!) or visible receiver cracks. I am of the opinion that the load I shot in NRA competition is low enough pressure that it could be used in one of these things, and I fired 168 Match with 39 grains IMR 4895/AA2495/H4895. This gave a velocity of 2532 fps out of a 26 inch barrel, never chronographed it in a shorter barrel. This is more powerful than a 7.62 X39 to put it in prospective.
Old military bolt guns were built in an era before processes existed to remove non oxidizable containment's from the steel. so period steels are always weaker and suspect compared to modern metallurgy. However, do a search for cracked slides of modern 1911's on 1911forum.com, and it becomes obvious that the perfection of modern steels is still a ways off!
And remember, these receivers and bolts have been through one lifetime, maybe more, and you don't really know the fatigue lifetime remaining in the things. These rifles were obviously rebuilt and refurbished as a war reserve, I understand some issued to Police. No one expected heavy usage, were only to be issued if Spain was in a desperate condition.
Take it easy on the thing and always wear your shooting glasses. If the case head blows, gas is going straight in your face, and eyes!
