SEOUL, 15 May 2015 (AFP) - Straight birdies gave Norris and Moon a four-shot lead on seven under par on the hilly 6,353 metre (6,947 yard) course at the Namseoul Country Club.
Norris collected four birdies in the first nine holes and hit three bogies and two birdies on the second nine.
"It is a tough golf course ... You got to play smart and hit good shots. Commitment is really important around this course and that will be the key at the weekend, if you don't commit you get into big trouble," he said.
Unheralded Moon bogeyed the second and got birdies at fourth and eighth. He then went on a four-hole birdie blitz from the 13th and birdied the last hole to post 66.
Overnight leader Kim Young-Woong had a disappointing day, shooting 74.
The 16-year-old high-school student was four shots off the lead in third place, retaining his hope of winning the one billion won ($916,000) title.
A stroke further back was Gareth Paddison from New Zealand who shared fourth place with Martin Kim from Argentina and two Korean players.
The Maekyung Open has been a happy hunting ground for home players with Park Jun-Won becoming the 10th successive Korean winner of the title last year.
Leading second-round scores (South Korean unless stated, "A" denotes amateur):
137 - Moon Kyong-Jun 71-66, Jason Norris (AUS) 68-69
141 - Kim Young-Woong (A) 67-74
142 - An Jae-Hyun 71-71, Gareth Paddison (NZL) 69-73, Martin Kim (ARG) 71-71, Choi Jin-Ho 72-70
143 - Nathan Holman (AUS) 72-71, Lee Tae-Hee 71-72, Lee Jae-Kyeoung (A) 73-70, Kim Do-Hoon 76-67