Its a Spanish 1916 Guarda Civil Mauser, originally 7mm rechambered for 7.62 CETME as somebody said earlier, NOT 7.62 NATO!
They were available all over the place for $100 or less 20 years ago, and many dealers and jobbers were selling them as chambered for “.308.”
I bought one about 20 years ago, and a box of commercial .308, THEN researched it and sold it without firing it after I found out what it really was.
The 7.62 CETME round is the round originally developed by H&K right after WWII for their CETME assault rifle that eventually became the HK 91, but since they were by law not allowed to produce guns in Germany right after the war, they made it in Spain and Spain ultimately adopted it in the early to mid 1950s and the Rifle was also called the CETME. Spain was poor, could not afford a lot of the then State of the art CETME rifles, so they converted a lot of Spanish Army LARGE Ring Mauser (M98s) to the round, for training, some looking like modern assault rifles with fake gas systems at the front. The Guarda Civil (Spanish National Police) converted many of their older SMALL ring Mausers (M96s) also to the CETME round, which they then called the M1916.
The CETME round was tested by a lot of countries, including the US, who was looking for a “smaller” round than the .30-06 and a higher power/pressure round with a new powder based on the same dimensions as the CETME round was adopted as the 7.62 NATO in the late 1950s. The .308 Winchester, loaded even hotter, was then later developed commercially from the same 7.62 NATO round in the early 1960s.
They will all chamber in any gun made for any of them as they are dimensionally identical, but NOT in power! The CETME round is in the 45000-48000 psi(or CUP, I forget, but you get the relative power idea) chamber pressure range, the NATO round is loaded in the 55000+ range and the commercial .308 is loaded to the 60000+ range, something like 63,000.
Generally, it is not recommended to shoot commercial .308 ammo in a rifle originally designed for 7.62 NATO. It is also not recommended to shoot 7.62 NATO ammo in any rifle originally designed for or converted to 7.62 CETME, except POSSIBLY the LARGE ring converted Spanish Mausers.
(The later HK 91 is a much stronger version of the original Spanish CETME, but it’s tough to tell them apart at first glance...)
It could be catastrophic to shoot .308 Winchester ammo in the SMALL ring Spanish Mausers.
I am SO glad I didn’t!😎
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