Bottom line 7.62X51 NATO and commercial 308 Winchester should be considered a different caliber.
The 308 is over 10K CUP higher pressure and as mention should not be used in the Spanish 308 as it is called.
It can stretch the action leading to eventual failure and possible injury or worse.
Er on the side of caution and either use ammo marked with a the NATO cross inside a circle or loaded to about 40K CUP for hand loading.
As for the rear site, agree and a square file should open that up to improve ease of sighting.
"The right to bear arms should not be infringed upon if only to prevent tyranny in government". Thomas Jefferson, Constitutional debates