Rifle shooter Jack Rossiter has climbed from a sick bed to fire an Australian record in a vital step towards competing at his third Olympic Games.

Battling the 'flu, Rossiter didn't practice at all entering this weekend's Sydney Cup, part of Australia's shooting selection events for the Paris Olympics.

So the 26-year-old was shocked to create an Australian record in the 10m air rifle.

"It was unexpected," Rossiter told AAP on Sunday.

"I hadn't practiced for a week, I was in bed for three days straight, so I was just hoping to shoot well.

"I didn't have any expectations for Australian records or anything like that."

Rossister's triumphant Sydney score of 634.7 was two points better than the previous national benchmark set by Dane Sampson in 2019.

"I had the feeling I had to turn it up a bit because it is (Olympic) selections and you're always trying to do your best," Rossiter said.

The South Australian now sits atop the Olympic nomination leaderboard for Australia's men's 10m rifle team ahead of Sampson and Alex Hoberg.

Shooting Australia's selections for the Paris Games starting in late July won't be finalised until June but the 26-year-old is in pole position.

At the 2016 Rio Olympics, Rossiter was 46th in the 10m air rifle and at the Tokyo Games of 2021, he finished 29th in the 50m rifle 3 positions event.

"Rio was a long time ago, I was pretty young for that," he said.

"There's a massive contrast between how I prepare now as opposed to before. I am just a better shooter now than seven years ago.

"I have made some changes with training loads and just my approach to training in general as well as competitions.

"And it has really been beneficial over the past couple of years, I think I have been improving a lot from just before Tokyo."

In the women's 10m rifle, South Australian Charlotte Brand, who triumphed in Sydney, heads the Olympic nomination leaderboard.

Dual Olympian Elena Galiabovitch is frontrunner in the women's 10m air pistol with Bailey Groves the leader in the men's equivalent. Both were among weekend winners in Sydney.

Other victors included Tokyo Olympian Laetisha Scanlan in the women's trap while Mitch Iles, the grandson of clay target Hall of Famer Billy Iles, won the men's trap in his quest to make his second Olympics.