So what can you smart people tell me besides I probably shouldn't collect random vintage bullets to guns I don't own? Then again what better excuse to buy a vintage rifle than already having ammo for it?

NATO standard ammo is 7.62 X 51 MM and it is the same size as .308 with case thickness and pressure differences. The FN FAL fires the NATO round. 7.62 X 54 MM is the Russian rimmed round used in the Moisin Nagant, SVD and the PK family of Russian machineguns. It would help if you had a picture of the round next to a .308 round for comparison, but it sounds like you have a 7.65 Argentine/ Belgian Mauser (7.65 X 53 MM) round. The case length should be just a little longer (less than 1/8") longer than the .308's brass.kanata67 wrote:" Argentine FAL 7.62x55 NATO caliber.
The Argentine Armed Forces officially adopted the FN FAL in 1955, but the first FN made examples did not arrive in Argentina until the autumn of 1958. Subsequently, in 1960, licensed production of FALs began and continued until the mid to late 1990s, when production ceased.
Argentine FALs were produced by the government-owned arsenal FM (Fabricaciones Militares) at the Fabrica Militar de Armas Portatiles "Domingo Matheu" (FMAP "DM")in Fray Luis Beltrn, located a few miles north of Rosario. The acronym "FAL" was kept, its translation being "Fusil Automatico Liviano", (Light Automatic Rifle). Production weapons included "Standard" and "Para" (folding buttstock) versions. Military rifles were produced with the full auto fire option. The rifles were usually known as the FM FAL, for the "Fabricaciones Militares" brand name."
Found this info. I always thought FAL were 7.61x51. If the rounds were made in 1935 and this version FAL didn't exist till the late 50's what were they originally used in?