The 27-year-old Sydneysider moved up from tied-ninth to joint-second at the halfway point and trails American Ben Griffin by two shots.
Starting on the back nine at the Country Club of Jackson on Friday, Endycott had an eagle on the par-5 third, birdies on holes 7 through 10 plus 13 and 17, but finished with his lone bogey on the 18th.
"Game has just been trending in the right spot, and it was nice to play well the last couple days," Endycott said.
"I absolutely crushed this drive down 9, hit the power line and forced me to reload, and hit probably one of the worst golf shots I think anyone would have hit this week.
"It worked out good, caught the fairway and made birdie. It was meant to be."
The tournament is part of the FedEx Cup Fall, with players trying to finish among the top 125 in the FedEx Cup to keep full PGA Tour cards for 2024.
Currently 129th, Endycott added he's "been really, really focused on what I'm trying to do right now", and was just happy to make the cut.
"That's what I said to my caddie; it's nice to have a job on the weekend. I was getting sick of flying home on Friday nights.
"I'm pretty proud of myself the way I managed myself around. I played awful here last year ... We'll go after it tomorrow."
He's one of four players at 12 under chasing Griffin, who went even lower than Endycott with a personal-best nine-under-par 63.
It was highlighted by a 65-foot eagle from the fringe on the par-5 14th hole.
Griffin is at No.66 and already has his card locked up, but has reason to succeed in the country's deep south.
"I'm primarily vegan. I'm plant-based, so it's the Sanderson Farms tournament, so it's kind of a funny one," he said.
"I just want the headline to say, 'Vegan wins chicken championship.' I mean, it's bad. But I've got to be honest with you guys, that's kind of a motivator for me. I think it would be kind of funny of a headline if I get it done."
At stake for him is to be among Nos. 51 to 60, which qualifies him for $20 million ($A31 million) tournaments early next year at Pebble Beach and Riviera.
First-round leader Chesson Hadley followed up his 64 with a 69 to be in a large group three shots behind.
Scoring was so low across the field that the cut came at five-under 139. Among those missing was defending champion Mackenzie Hughes (70) of Canada.
Aussies Cameron Percy (68) and Lucas Herbert (69) made it through to the weekend after finishing their first two rounds six and five under, respectively, but compatriot Greg Chalmers (74) missed the cut at one under.
With AP & Reuters.
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