The defending Xfinity champion led 110 of 200 laps to win for the second time this season and the second time in three races. He finished more than two seconds ahead of Justin Allgaier. Jeffrey Earnhardt was third, followed by Noah Gragson and Justin Haley.
Reddick, a 23-year-old in his first season with Richard Childress Racing, had had eight consecutive top four finishes.
"He has a talent," owner Richard Childress said. "He will be a superstar in the (NASCAR) cup division and we want him to do it for RCR."
Reddick showed that at Charlotte Motor Speedway. On a hot, humid afternoon where several competitors including lap leaders Christopher Bell and Brandon Jones were sliding into the wall, Reddick kept himself cool and collected.
"I felt great all race long," Reddick said.
Reddick moved in front for on the lap 72 and held on to win the second of three stages. He was ahead much of the final, 110-lap stretch and made it through several restarts. He gambled during one caution period, coming in to take four tires to fall off the lead. Reddick bounced back quickly to pass John Hunter Nemecheck and pull away from the field.
Reddick fell behind Cole Custer on a restart with 23 laps to go before a final caution - brought out by a spinning Josh Williams - bunched the field. Reddick broke from the group quickly as Custer spun his wheels and fell behind.
No one had enough to catch Reddick, who won for the fifth time in 62 career Xfinity races.
Reddick said he hasn't been so consistent since he was a 10-year-old racing karts in California. "It's awesome," he said. "Hopefully, it means the next couple are going to keep rolling this way."
Reddick figured to get a challenge from Bell, who won the pole by nearly two-tenths of a second and looked like a strong bet to win his second straight Xfinity race and fourth of the season. Bell took the opening stage and was running strongly until things went wrong at the end of the race's second segment as hit the wall in turn four while running second and damaged his right front tire. Bell stayed out on the track despite losing track position as his tire shredded and caught fire in the pits.
Bell hurried out of his car as his tire burned. The car went behind the wall for good.
Reddick prevailed on a hot, humid day where temperatures climbed to the mid-90s and car cockpits were close to 130 degrees. Earnhardt was slumped against his car after getting out, catching his breath and trying to cool off. Earnhardt was taken the infield care center where he was checked out and released.
Austin Dillon, the 2017 Coca-Cola 600 winner, took part in the Xfinity race, but exited the car during a caution with 40 laps left due to the heat. Dillon will start fourth in Sunday in NASCAR's longest race.
Gragson said he came through the heat - and 300 miles of racing - in good condition. "I was kind of questioning my conditioning," he said. "Not so much now."
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