Denny McCarthy set a 36-hole course record at the TPC River Highlands only for 2011 PGA champion Keegan Bradley to match his total hours later, the pair sitting on 15-under par at the midway point at the Travelers Championship.
McCarthy followed Thursday afternoon's red-hot round of 60 with a five-under 65 on Friday morning.
He recovered from a bogey on the second hole, his first dropped stroke of the tournament, rattling in six birdies thereafter.
Bradley, meanwhile, hit five birdies on the trot on the back nine to follow his opening 62 with a 63 on Friday.
They sit two strokes clear of Chez Reavie in third spot, with Eric Cole a further two back on -11.
Rory McIlroy lies seven strokes adrift in tied-10th, though it could have been much better for the US Open runner-up who was seven-under thru 12 after a blistering run around the turn on Friday.
Ultimately, a costly double-bogey on the penultimate hole would hamper his challenge, leaving him some way back from the leading pair.
Beginning on the 10th, McIlroy reached the turn in 30, with birdies arriving at 11, 14, 15, 17 and 18. Two more birdies followed on 2 and 3, with another coming at the 6th to push the four-time major winner to 10-under overall.
However, his slip-up at the 8th saw him fall back to eight-under, in a group that also included Norway's Viktor Hovland (65) and defending champion Xander Schauffele (64).
"I hit a pretty good shot, I just misjudged the wind a little bit and it came up short in the one place you couldn't miss today," said McIlroy. "Other than that, it was a really good round of golf."
One stroke further back is compatriot Shane Lowry, who followed a fine 64 on Thursday with a more humdrum effort of 69 on Day 2.
The 2019 Open champion struggled to an even par outward nine of 35 with birdies on 11 and 15 cancelled out by dropped strokes on 14 and 17. A solitary birdie on the way home on the short fifth hole would leave him under par for the day.
Seamus Power is tied-68th on three-under after rounds of 69 and 68 over the opening two days.
Jon Rahm of Spain followed an opening 67 with a 71 and missed the four-under-par cut line by two shots. It was the World No. 2's first missed cut since September 2021, ending a streak of 32 made cuts, (not counting his withdrawal after one round of The Players Championship due to illness).
