Justin Bolli posted a 6-under 66 and is alone in second place at minus-15.
Second-round leader Gabriel Hjertstedt managed a 3-under 69 and is tied for third place with John Merrick, who carded a 4-under 68 on Saturday. The pair is knotted at 13-under-par 203.
Buckle collected his first birdie at the par-5 fifth when his 10-footer found the bottom of the cup. He reeled off three birdies in a row from the seventh, ranging in distances from 3 feet to 30 feet.
Buckle was still not threatening the top of the leaderboard, but a birdie at the par-5 12th inched him closer. It was his play at the end of the round that got Buckle into the lead.
At the par-4 15th, Buckle hit a sand-wedge to 20 feet to set up birdie. He tapped in a short birdie putt at the 16th, then polished off another three birdies in a row with an 8-foot birdie putt at 17.
All totaled, Buckle obliterated the former tournament 54-hole mark by four shots. Kyle Thompson set the record of 203 two years ago, but now Buckle gets his name in the history book.
'You have to putt well to shoot good scores,' said Buckle. 'The weather was perfect for scoring. You just make as many birdies as you can. Today was great.'
Buckle is not just a tour rookie, he has yet to play in the United States this season. He participated in the Jacob's Creek Open Championship and New Zealand PGA Championship, but finally came over to the States, where he earned his Nationwide Tour card through Q-school.
'The jet lag was tough,' admitted Buckle. 'I'm just starting to feel normal.'
Michael Long and Brendon de Jonge both posted rounds of 3-under 69 on Saturday. They are tied for fifth place at 11-under-par 205.
Brian Smock (66), Michael Putnam (68), Ryan Armour (68) and Michael Sim (69) are knotted in seventh place at minus-10.