The career-best round puts Harry Hall three shots ahead of the field at Colonial Country Club.
Hall took only 22 putts to card a score of eight under and a decisive three-shot lead in Fort Worth, Texas.
He picked up eight birdies without dropping a shot and managed to save par from 15 and 30 feet.
Harris English is Hall's closest competitor on five under, after the American split a bogey with six birdies, including two on his final two holes.
After his round, Hall revealed he played no less than 36 holes of practice at Colonial this week before he teed off on Thursday.
"Maybe that's the key, just to see a bit more of the course than I have done in the past," said Hall, as per pgatour.com.
"I didn't do too much different. I kind of just made things a little bit more simple.
"I was really in the moment out there and determined to play some good golf. The 7 out of 7 scrambles doesn't really surprise me because that's the best part of my game, but the way I hit the ball the first two-thirds of that round was pretty special."
Tom Hoge, Adam Schenk, Robby Shelton and Andrew Putnam are all tied for third on four under par.
Elsewhere, it was a mixed day for Scotland's Russel Knox and English duo Callum Tarren and Justin Rose, who all head into Friday's second round on one under.
Club professional Michael Block, who dazzled the golfing world with his heroics at the US PGA Championship heroics, had a rough outing as he finished his opening round 11 over par, his worst score of the year on the PGA Tour.
"If you are a golfer, you've had the day I've had," said the American.
"You understand the facts of where the lies aren't good and the trees are in your way every time. Even your good shots are bad, your bad shots are worse.
"It is what it is. I'm going to live with it. I thought it was going to happen that third or fourth round last week at Oak Hill, and it never happened. It happened now, and I wasn't surprised by it, to tell you the truth."
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