Ello there. I Am a American Carbine or known as the M4A1. I am a AR-15 style rifle, and my caliber is 5.56 mm, the cartridges i use is the 5.56x45mm NATO. And my barrel is 14.5 inches. I have 2 similar brothers, or known as the AR-15, and M16A1 or M16. While the AR-15 has single shots, M16 has a burst function. and I am automatic. And my service start was in 1994, I do call myself, female.