The 33-year old from Hamsphire won the same layout where he had won the gold medal in the 2000 Olympics.
He record a total of 188 hits, including 47 out of 50 targets in the final round.
"It's destiny," Faulds said.
"I had never came back to shoot here in Sydney, after my victory at the 2000 Games."
"It has been quite difficult.
"I had no idea that I was in the lead, while I was shooting.
"I had the feeling, but I tried not to watch the scoreboard, to keep the focus on my targets.
"I am extremely happy about winning this quota.
"I had a bad season last year.
"I changed my gun and I had it took some times to get used to it."
It was his first victory in an ISSF World Cup since Suhl, Germany, three years ago.
Among those Faulds beat was Australia's Russell Mark, the 1996 Atlanta Olympic champion, who narrowly missed the chance to also book a quota place for London.
American world number one Joshua Richmond, who claimed the silver, ahead of Italian Francesco Daniello in third.
That mean Daniello claimed the other quota place on offer for London 2012 as Richmond had already won one earlier for the US.
March 2011: ISSF World Cup in Sydney attracts record participation