By Ian Ransom

RIO DE JANEIRO (Reuters) - A breath of wind, a shaky floorboard or an untimely attack of nerves can all affect the fickle flights of arrows but nothing could stop Ku Bon-chan as he unleashed a perfect volley to drive South Korea to the men's team gold at the Rio Olympics.

In a mouth-watering final against a powerful United States team, with rowdy fans shrieking from the terraces at the Sambodromo, the 23-year-old entered a bubble of calm and shot all six of his arrows plum in the center of the target.

The six perfect 10's, called each time by a booming loudspeaker and greeted with roars from the crowd, were a death knell to the Americans' hopes of gold and redemption for their defeat in the London final four years ago to Italy.

Ku, however, was oblivious to it all.

"I actually did not know I had the perfect score six consecutive times," the archer, a member of a university team in North Gyeongsang province, told reporters through a translator.

"So they told me later after the game was done, but I was very happy."

Ku was the best performer in a team of world championship winners. But only just.

Kim Woo-jin, who dazzled his rivals with a 72-hole world record during the ranking rounds on Friday, took maximum points with five of his six arrows.

Lee Seung-yun hardly let the team down by nailing 10's on four shots.

Taking to the raised shooting platform at the Sambodromo, the three led off the final with six 10's in succession, a decisive statement of intent that the United States were unable to match.

The American trio of Brady Ellison, Jake Kaminski and Zach Garrett shot well in defeat but still finished on the wrong end of a stinging 6-0 scoreline.

"Incredible what they did," said Team USA's head coach Lee Ki-sik, the mentor of four Korean Olympic teams from 1984-1996.

"I never thought the Koreans could shoot that great. Korea never had so strong a men’s team.”

It was sweet validation for South Korea, who were dumped out of the semi-finals in London by a U.S. team that featured Ellison and Kaminski.

The bronze they won was considered something of a failure.

None of that team made it back to Rio, buried by the relentless treadmill of elite archers from a country that has won 20 Olympic titles since archery returned in its modern form in 1972.

The team kissed their medals and savored the moment, knowing full well that it may be their last trip to an Olympics.

The treadmill will crank up again ahead of the Tokyo Games in 2020.

(Editing by Peter Rutherford)