Keselowski battled Chastain for the lead after passing Harvick for position on a restart, but he made contact with the wall attempting to overtake the young gun for the lead.
Cole Custer was second and Tyler Reddick third. Hamlin led the first 12 laps before Larson passed him.
Brad Keselowski won the 500 to become the year’s 10th victor, joining Kyle and Kurt Busch, Kevin Harvick, Martin Truex Jr., Clint Bowyer, race runner-up Joey Logano, Chase Elliott, Erik Jones and Austin Dillon. Harvick blamed Chastain for the wreck and said the 25-year-old probably would not get the chance to drive too many races like this in the future. Chastain retook his lead on Lap 71. It was Larson’s seventh top three finish this year.
“At a place like Darlington, where things kind of move around, I think you might be able to take some”, he said when asked about applying any lessons learned to the Southern 500.
Larson thought he had a better auto than Hamlin for much of qualifying, but lost a bit of grip in between the first and second turns to cost him the pole.
Chase Elliott was fourth and Erik Jones fifth.
NBCSN wraps up on-site coverage at 10:30 p.m. ET with a trackside post-race show, before throwing to Stamford, Conn., for Victory Lap at 11 p.m. ET hosted by Carolyn Manno (@carolynmanno) and NBCSports.com lead motorsports writer Nate Ryan (@nateryan).
Keselowski drove away on the restart with 19 laps to go. Other short odds to win are Kyle Busch (+325), Martin Truex Jr. Joey Logano was fourth followed by Brad Keselowski, the Xfinity victor here Saturday, in fifth.
The race was delayed 45 minutes because of the threat of bad weather spotted near the track.
WEATHER DELAY: Darlington officials twice had to clear the grandstands because of potential severe weather threatening the area.
Ross Chastain has earned his first career pole in the Xfinity series when he finished on top in qualifying at Darlington Raceway.
The race is scheduled for 367 laps on the 1.366-mile egg-shaped layout.
He’s off to a good start on the weekend by winning the pole Saturday for the Southern 500.
Legendary team owner Jack Roush and several members of the NASCAR Hall of Fame, as well as Randy Poindexter, Senior VP of Marketing for Bojangles, will call for drivers to start their engines at 6:07 p.m.
In fact, Allgaier has been so successful in the No. 1 JRM Chevrolet that his boss, Dale Earnhardt Jr., recently took to Twitter to tout his driver as deserving of a Monster Energy NASCAR Cup Series ride.
They also put Team Penske in victory lane here for first time in decades in a race that has become the sports’ Old Timer’s Day to celebrate its history. Hamlin’s been even more dominant in Darlington’s Xfinity races, with five victories in his last eight starts.
Until Sunday night at Darlington Raceway, though, he was a somewhat-comfortable fifth in points among winless drivers.
“So, you’ve got a really inexperienced guy in a really fast vehicle and made a really bad move, and then wrecked me down the back straightaway and hooked me to the right”. (4 wins, 27 playoff points) and Clint Bowyer (2 wins, 10 playoff points). However, because there is no way by which he can fall below the playoff cut line in the final race of the regular season, he has secured a playoff berth. The defending victor finished in the top 5 the last three weeks and posted the top speed in the first practice session at Darlington this weekend.