Is it possible you mean an AR 15 made with an elcectroless nickel finish?

catching fire is 17 ar points and mockingjay is 15 i think :)

The AR-15 was created by a design team led by Eugene Stoner. Initially, the AR-15 was intended to be a companion rifle to the AR-10; the AR-10 was intended to replace the M1 Garand while the AR-15 was intended to replace the M1, M2, and M3 carbines.

The AR 15 is a rifle, not a caliber. the .223 is a caliber. Usually the AR-15 is made in caliber .223.

The M3 is the semi-automatic version of the Ar-15 (M4).