'Ten birdies, you don't do that too often,' said Sheehan, whose previous low round was a 65. 'But it doesn't mean anything really, it is just a good start.'
Zoran Zorkic and Michael Connell share second place at 7-under-par.
Sheehan birdied his first two holes at Highland Springs Country Club before parring the next three. From there, Sheehan moved up the leaderboard with three consecutive birdies, starting at the sixth.
Sheehan put his tee ball in the water at the ninth and never recovered, dropping his only shot of the round. He rebounded with five birdies on his second nine for the two-shot lead.
'There is always a little luck involved in a round like this,' said Sheehan. 'But with the exception of one bad shot off the tee at the ninth hole, I hit the ball really well all day.'
Zorkic played remarkably well considering the glue on his driver came off Wednesday and he played the round never trusting the club.
'I used a driver today that didn't work very well,' said Zorkic, who still managed to hit 10 of 14 fairways. 'The glue came apart in my driver yesterday, and I didn't feel comfortable with it at all today. It took me out of the par-5s, which out here you have to take advantage of.'
Connell, a Monday qualifier, tallied five consecutive birdies around the turn to move up the leaderboard. He collected three birdies from the 15th to match Sheehan in first but ran into trouble at the 18th.
He knocked his tee shot out of bounds at the par-5 closing hole and never recovered, double-bogeying the hole to join Zorkic in a tie for second.
'I hit my tee ball solid on the last hole but it hit a tree and went out of bounds,' Connell said. 'But overall I am still pleased with how I played today.'
Full-field scores from the Ramey Price Cutter Charity Champ.