Sydneysider Endycott, who ended 2023 by winning the fiercely contested PGA Tour Q-School in Florida, shot a four-under 68 at Royal Golf Club to move to within two shots of the halfway lead shared by Sweden's Jesper Svensson, Swiss Joel Girrbach and South African Dylan Frittelli.
There was rarely a dull moment in the 27-year-old's round on a blustery day in the European Tour event as Endycott recorded nine birdies to go with three bogeys and one double bogey.
That double came at just the short second hole when Endycott found the desert with his drive and went into the rough with his next before taking three more to get down.
Far from dismaying him, he just seemed inspired, hitting his next 103-yard approach at the par-five third to within five inches of the hole.
Five more birdies followed in the next seven holes as he raced up the leaderboard, but two bogeys in the next three holes checked his dramatic progress.
Again he rebounded straight away, holing an 11-foot birdie putt, then an even better one from 22 foot to recoup his losses.
A lovely 100-yard approach from the rough to four feet at the 17th was his last dramatic act of the day.
Still, Endycott couldn't match Swede Svensson, who recorded the lowest round of the day with a seven-under-par 65 to hit the top after starting six off the lead.
"It was tough out there," Svensson said of the strong winds.
"I set from the beginning to play quite conservative and we were playing for the big targets. For the first part of the round it felt like every time I had the putter it had a chance of going in so it was nice."
Girrbach carded a two-under 70 and Frittelli birdied the last for a four-under 68, as France's overnight leader Tom Vaillant slipped back to a five-way tie for fifth alongside Endycott, South African Ockie Strydom, Frenchman Julien Gerrier, and Welshman Jamie Donaldson.
That group were a stroke behind Spain's Alejandro Del Rey, who was one shot off the leading trio after his two-under 70.
Other Australians in the field didn't fare so well, with David Micheluzzi's 74 and Jason Scrivener's 73 putting them on level par for the tournament, in a tie for 58th position.
