If anyone can hable Espanol you will read that the Spaniards intended the Guardia M1916, the FR7 and the FR8 to be used with bothe the CETME cartridge and 7.62 NATO cartridges. The original importer had HP White Lab test them and found no problems using 7.62 NATO. Many of them have "7.62 NATO" stamped on the side of the reciever as the cartridge to use. The CETME cartridge was designed for the CETME rifle, a rifle designed by German engineers as a upgraded STG44 to fire the 7.62 NATO cartridge. The problem was at 7.62 pressures the case was still gripping the chamber during extraction and there were many malfunctions in the already fielded CETME rifles. The M1916, FR7 and FR8s were already fielded also and were working fine with 7.62 NATO ammunition. It was the CETME rifles that were having problems. The temporary solution for the CETME rifle was a lower pressured cartridge, i.e. the 7.62 CETME cartridge which is the same case as the 7.62 NATO but with a lighter bullet at lower pressure. Of course these Cetme cartridges shot ok in the M1916, FR7 and FR8 rifles also. The final solution for the CETME rifles was a recall for rebarreling that had fluted chambers. The CETME design transitioned into the G1/G3 rifles of German manufacture. This is all documented by the german engineers who designed the CETME rifle and is available in the internet and in other resource historical books. The CETME cartridge WAS NOT designed for the M1916, FR7 or FR8 rifles. Nor were those rifles made for the CETME cartridge. The rifles came before the CETME cartridge. The M1916, FR7 and FR8 rifles were fully intended to be used with 7.62 NATO ammo as stated in the Spanish manual.
Whether anyone wants to shoot 7.62 NATO or .308 Winchester in their M1916, FR7 or FR8 is their choice. I just have to disagree with the mistaken concept that these actions, particularly SR Mauser actions, were "designed" for a weaker cartridge. They were not and that is another myth.
Larry Gibson