Six of Horne's birdies came over the final 10 holes as he claimed a 1-stroke lead over Peter Hanson, who rode a string of four consecutive birdies on Nos. 14-17 into second place.
Horne had a birdie at No. 2 and was still 1-under after eight holes before beginning his charge with a birdie at the 580-yard, par-5 ninth hole. He jumped up the leaderboard with three consecutive birdies at Nos. 11-13 and finished with two more birdies over his final three holes.
Henson was 2-under after a bogey at No. 13. He then ran off four straight birdies and pulled within one stroke of Horne.