There are a lot of rifles out there that do not have as good gas handling as the 98 Mauser, but that hasn't kept Winchester from selling a lot of guns. (ref Frank DeHaas.)
Once upon a time, it was said that the Spanish Mauser conversions were meant for 7.62 CETME ammunition, Spanish GI 1958-1974 (Hogg & Weeks.) The CETME round was the same case as 7.62 NATO/.308 Win but lighter loaded. Handbook STARTING LOADS for .308 are close.
For some reason the Internet Community has concluded that this is not so, that the Spanish intended to use full power NATO ammo in them all along. I have not seen a reference for this change in position.
Either way, I figure that the conversions of 1916s, and rebuilds to FR7 and FR8 were meant for people who would not be doing a lot of shooting. Border guards, line of supply troops, etc. Not like American gun nuts who blast away every weekend as long as the cheap ammo holds out.