does it have a lot of red on the back? because if so, it is probably a rooster. I am just bringing up some BCMs right now, and i find them very hard to sex. They are the only chicks i have no ideas how will turn out. Mine are about 8-9 weeks now. I could tell my other breeds between 2-5 weeks, and the only one that fooled me was a buff japanese banty that suddenly drew a massive comb on week 9.
My BCM that is male for sure, is SO male, HUGE comb/wattles, flaming red, lots of copper, massively bigger, expecially the legs and feet, and then nearly all the others have combs/wattles in varying degree of redness, and i think the ones with a lot of red on their back are male, the others i am not so sure. I got 9 straight run from a breeder... they could all be male, but that would be fairly unlikely ... i hope!