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Spain was another country going for NATO standardization, and were the very first to develop and adopt the CETME Modelo 58, ergo the very first iteration of what most people now think of as the Heckler & Koch Gewehr 3.
They had all these old Mauser rifles around still, though, and mostly 98 action ones, some being 93 actions. Transitioning towards 7.62mm NATO, they get that idea to convert their old Mauser rifles to the new cartridge, and then having it as the stopgap rifle while the army is busy arming up with the new CETME rifle. Enter the FR-7 (Mauser 93 action) and FR-8 (Mauser 98 action).
Not just rebarreled for 7.62mm NATO, they have a slightly shorter barrel than before, also bearing the flash hider of the CETME rifle, along with an imitation cocking-tube under the barrel (which you can store some cleaning gear inside of), all to enable the use of the standard CETME bayonet as well as standard 22mm NATO rifle grenades. The new sights are also meant to imitate those of the CETME.
The resulting rifle is light, somewhat loud, but quite functional, and compatible with the 7.62mm NATO and 7.62mm CETME cartridges (the latter being a somewhat lighter load Spain aimed for initially, before deciding to just go for the regular one anyway).