Rookie Ryggs Johnston looking a lethal weapon until 14th hole at Australian Open

American Ryggs Johnston claimed a share of the lead heading into the final round of just his second DP World Tour event at the ISPS HANDA Australian Open.

The Qualifying School graduate, named after Mel Gibson's character in the Lethal Weapon films, carded a four-under-par 68 at a rain-soaked Kingston Heath to catch Lucas Herbert on 14 under par.

Home favourite Herbert had cruised into a four-shot halfway lead, but produced only one birdie in a level-par 72.

Johnston made four straight birdies from the fourth, a run completed with a stunning approach to the seventh.

Further gains followed at the ninth and 12th, putting the Montana native on course to claim the outright lead heading into Sunday.

However, he ran up a double-bogey seven at the 14th after a wayward drive down the right and firing a bunker shot over the back of the green.

Three-time DP World Tour winner Herbert endured a cold putter on the back nine, while Johnston saw a lengthy birdie effort on the last lip out.

"It would be huge for me to win for my career," said Johnston.

"I’m trying to keep as much pressure off myself as I can. So just trying to go out there and just play good golf and whatever happens, happens."

Five players are tied for third with China’s Wenyi Ding, Finland’s Oliver Lindell, Chile’s Joaquin Niemann and Australian pair Elvis Smylie and Jasper Stubbs all on 12 under.

Ire'and's Gary Hurley missed the cut on Friday.