Colossus is young, but 24's not too young to lead a squad. There are younger Lieutenants and similar leadership ranks in the military. Also he's been a field member of the X-Men since he joined at 16 due to basically being an indestructible tank on legs. So he's been in constant action for 8 years.<br/><br/>However, leadership is the last thing Colossus wants, but he will in emergencies or if Bishop or whoever else is unable.