Gainey was joined atop the leaderboard by Matt Weibring and Kris Cox.
There is a six-way logjam in fourth place. Australians Cameron Percy and David Lutterus share fourth place with Brian Stuard, Michael Boyd, Jason Dufner and Justin Hicks at 4-under 66.
Gainey, known for his unique style of wearing two gloves, dropped in back-to- back birdies from the 11th at Hardscrabble Country Club. After he dropped a shot on 13 due to a double-hit on a chip, Gainey came right back to birdie 14 and 15.
After a pair of pars, Gainey birdied three in a row from the 18th to jump to minus-6, including a chip-in birdie on the first. He parred his final seven holes to end there.
'Frustration has really set in for me. The year has been real sketchy for me,' admitted Gainey, who has made three cuts in nine starts as a rookie on the PGA TOUR. 'I have hit it good all year except for maybe three rounds. I have not made any putts and my scores show that.'
Both Weibring and Cox carded bogey-free rounds. Weibring started with birdies on 12, 14 and 16. He moved to minus-four with a birdie on the par-5 third. He eagled the next par-5, No. 5, to gain a share of the lead.
'I played really good today. I drove it well, I putted well,' Weibring stated. 'I had only a couple of those five-footers for par and I made those. Those are important to make to keep things going.'
Cox, like his fellow leaders, played the back nine first. He first three birdies came at 11, 13 and 17.
On the front nine, he ran off three birdies in a four-hole span from the third to jump into a share of the lead. He parred the last three to end there.
'That's probably the best I've hit it in two years,' said Cox, who has missed the cut in all eight of his starts this year. 'I've just had a hard time playing this year. I haven't played well all year. You play so poorly you wonder if you're ever to be good again. I played like a pro today.'
Darron Stiles, the 2006 champion, leads a large group tied for 10th at 3- under 67. He was joined there by Josh Broadaway, Ty Tryon, Jim Herman, Anders Hultman, Won Joon Lee, David Morland IV, Rich Morris, Steve Schneiter and Jason Schultz.