7.62x51 NATO...(known as .308 Win. in the states for civilian use).....as stated it is Portugese.
Roughly 15 years ago this was coming into the country for CHEAP, when many countries switched from that into 5.56x45 platform battlerifles.
I was buying it by the 1000 rd case, filled with five 200 rd vinyl "battlepacks" for less than 18 cents a round to feed a collection of FN-FAL's....those were the days. Probably went thru 20,000 rds of that stuff.
Once the surplus from Germany (DAG), England (RG) and Portugal dried up, so did shooting the FAL's!