Billy Horschel fired a six-under par 64 on Friday to join a four-way tie atop a jammed leaderboard at the PGA Tour's Wyndham Championship.
Horschel, chasing a sixth tour title and his first since the 2018 Zurich Classic of New Orleans, hit 13 of 14 fairways and 16 of 18 greens in regulation to finish 36 holes on 10-under par 130 - tied with former Wyndham champion Kim Si-woo of South Korea and Americans Tom Hoge and Talor Gooch.
Kim, who notched the first of his two tour titles at the 2016 Wyndham, had six birdies in his five-under 65. Gooch also posted a 65 while Hoge followed up a first-round 62 with a 68.
Harold Varner, who shared the overnight lead with Hoge and Canadian Roger Sloan, carded a 69 to join a group on 131 that also included Ireland's Shane Lowry (63), Harris English (67), Andrew Landry (65) and Doc Redman (64).
Sloan was among another seven players a further stroke back on 132 - with a total of 25 players within three strokes of the lead at Sedgefield Country Club in Greensboro, North Carolina.
Horschel, who out-duelled Rory McIlroy in the final round of the 2014 Tour Championship to claim that year's FedEx Cup playoff crown, said work on his game over the past two years was paying off in the final event before this season's tour playoffs begin.
"I just put the ball in the fairway, which is a big key," he said. "If you can put the ball in the fairway around here you can be aggressive to these pins. You've got a lot of scoreable clubs into it.
"I don't think I made a lot of putts," added Horschel, whose longest birdie putt was a 16-footer at the sixth - his 15th hole of the day. That followed two-foot birdies at the fourth and fifth and he capped his round with a seven-foot birdie at the ninth.
"I hit a lot of close shots and easy birdies. It was a really nice, solid round of golf -- effortless 64."
Kim also teed off on 10 and parred his first nine holes before a birdie from the fringe at the first.
He followed a bogey at the second with birdies at four, five and six and capped his round with birdies at eight and nine. He didn't miss a putt from within 10 feet.
After thunderstorms halted play early on Thursday, tournament officials were bracing for more bad weather on Saturday, with tee times moved up in hopes of completing the third round before storms arrived.
Despite the wealth of low scores on the rain-softened course, well-known names who failed to make the cut included world number seven Brooks Koepka and England's 17th-ranked Justin Rose.
Leading scores on Friday after the second round of the PGA Tour Wyndham Championship in Greensboro, North Carolina (USA unless noted, par-70):
130 - Tom Hoge 62-68, Kim Si-woo (KOR) 65-65, Talor Gooch 65-65, Billy Horschel 66-64
131 - Harris English 64-67, Shane Lowry (IRL) 68-63, Andrew Landry 66-65, Doc Redman 67-64, Harold Varner 62-69
132 - Roger Sloan (CAN) 62-70, C.T. Pan (TPE) 68-64, Mark Hubbard 67-65, Rob Oppenheim 66-66, Jason Kokrak 69-63, Webb Simpson 66-66, Tyler Duncan 68-64
133 - Peter Malnati 68-65, Patrick Reed 65-68, Paul Casey (ENG) 67-66, Kevin Kisner 69-64, Ryan Brehm 64-69, Adam Long 68-65, Im Sung-jae (KOR) 69-64, Patton Kizzire 66-67, Tommy Fleetwood (ENG) 69-64