PINAWA, MANITOBA -- Duffers across North America are shipping golf balls to the Whiteshell Nuclear Research Establishment for a free blast of gamma rays.

The reason?

Scientists have discovered zapping the balls gives them extra bounce.

The technique is used to toughen rubber in radial tires and to make plastic components for cars and planes. With two-piece golf balls, as opposed to the wound type, the process leads to longer shots.

"If you're really a hard hitter who hits 300 yards, you'll get 5 percent -- you're looking at 15 more yards," said Larry Christie, an ardent golfer and spokesman for the lab.

He said nuclear researchers at Whiteshell, operated by Atomic Energy of Canada, have been irradiating golf balls for some time. "There have always been scientists who were golfers, and from time to time they would pass balls through the linear accelerator. When I heard about this, I said, 'Well there's a lot of golfers out there who could benefit from this.' "

Although the gamma ray effect hasn't been advertised, word spread so quickly that the agency has treated several thousand balls in a year and a half.

The process does not alter the appearance of the balls, but the laboratory offers to stamp them with an identifying mark. Despite a U.S. Golf Association ruling that irradiated balls are acceptable for use, most golfers have chosen to keep their secret to themselves. "I don't know what that tells you about golfers -- I think it tells you they're competitors," said Christie.

Golfers have mixed reactions.

"I hate to condemn the ball but I didn't notice much difference," said weekend golfer Harold St. John. Golfing partner Ralph Lee was more enthusiastic: "I got a real good feeling from the ball, from the contact with it. Its carrying distance seemed to be a bit farther, after it landed. I got a pretty good roll out of it."