ID my ammo

[Headless Thompson Gunner]

I found about 100 rounds of loose ammunition in the bottom of my range bag the other day. I can't for the life of me remember what kind it is, where it came from, or how it ended up in the bottom of my bag.

It looks suspiciously like surplus 308. The headstamp reads "FNM 80-10", with that little 'circle plus' NATO logo. It has green primer sealant.

Anyone know what kinda ammo this is?

 

[SMLE]

You're right about it being 7.62/308. It's Portugese, "80-10" means October 1980, year and month of manufacture.