Bob Rhinehart's figures told him that a 6-to-1 shot named Samies Jug was the best bet of the night at Los Alamitos Race Course. He wagered accordingly, and then had to endure the excruciation that accompanies almost every bet on a quarter horse race.

Samies Jugs and his nine rivals made a 400-yard cavalry charge down the stretch, and reached the finish line almost simultaneously. Rhinehart had to sweat out a seven-horse photo finish until the camera finally disclosed that he had won it. Samies Jug had prevailed by a head; he was four noses and two heads in front of the seventh-place horse.

"The first time I ever came out here," Rhinehart said, "I saw horses go under the wire together like that and I wondered: How could anybody win here?" But after devoting the last three years to handicapping the sport, he has a far different impression. "Now," he said, "I think you can't possibly lose here."

Rhinehart, 30, became one of the most successful bettors at the country's principal quarter horse track after playing thoroughbreds for years without notable success. Friends had told him that quarter horse racing was a much more beatable game, and after his initial doubts he saw that they were right. Certainly, it is a much simpler game.

"In thoroughbred racing," Rhinehart said, "there are so many variables, but here all they do is go from point A to point B. And the animal is much more consistent. It's ideal for gambling."

To judge how the animals will get from point A to point B, there are only two relevant factors: the horses' inherent speed and the trouble they may encounter on the way.

Rhinehart calculates speed figures that have to be much more precise than anything thoroughbred handicappers use. Working in hundredths of a second, he calculates a "track variant" for each race. This means he attempts to measure the effect of any external factors--such as changing winds or the fog that occasionally rolls across the track--on the horses' times.

Quarter horse handicappers also have to observe races more closely than their thoroughbred counterparts, because every detail is potentially important in an event that lasts for only 19 seconds or so. The type of commentary in a popular tip sheet sold at the track reflects this concern with minutiae: "Start the Game was fidgety in last; broke in and was righted to lose a few steps, lost path briefly when front-runner crossed in front at gap, finished with some late speed clear path."

To make such observations, Rhinehart said, "You've got to watch every horse individually, and that means you've got to watch the videotape of every race 10 times. I've tried to watch two horses at a time but you just can't do it--you blink and the race is over."

This is such an important part of quarter horse handicapping that a number of regulars bring portable video recorders and cameras to Los Alamitos so that they can make their own films of the track's films. Rhinehart stays up until 2 every morning watching all 10 races 10 times each, making note of horses who broke slowly, lugged in or lugged out, or were bumped or brushed. He attempts to translate each incident into hundredths of a second and then applies it to the horse's speed figure.

As the result of all his labors, Rhinehart finds horses who have edges in ability over their rivals--edges so narrow that a thoroughbred handicapper might think them inconsequential. But in quarter horse racing, Rhinehart said, "The horses are so consistent that those edges hold up in the long run." In those breathtaking seven-horse photo finishes, he expects to know which nose will hit the wire first.