1. (n.) A weapon (generally an assault rifle) chambered in 5.56 NATO caliber.
2. (adj.) of or in 5.56 NATO caliber.
2. (adj.) of or in 5.56 NATO caliber.
1. "I count three hostiles: two AK's and a five-five-sixer, over."
2. The new five-five-sixer HE round was especially effective against lightly-armored vehicles and personnel.
2. The new five-five-sixer HE round was especially effective against lightly-armored vehicles and personnel.
by Kirk0007 July 26, 2010