"For the British?"
No, he volunteered to fight Tories, initially serving under his neighbor, Joseph Winston. Patriots had mounted soldiers, too. That's what a dragoon was. He fought in battles against Banastre Tarleton, and at Guilford Courthouse, among other battles he experienced in North and South Carolina.
I assume the question springs from the mistaken notion that all Regulators went on to become loyalist or Tory. Not so. Many of the "Over The Mountain Men" who defeated the British at Kings Mountain were former Regulators.
I just connected dragoon with Tarleton's Green Dragoons. I Thought dragoon was a term the British used for thier calvery units.