Hamlin appeared to adhere to NASCAR's new rule of staying in your damaged car until safety crews arrive, and photos showed he was clearly on the apron when he banked the seat restraint off Harvick's car.
The accident happened as Hamlin was taking the high line through a turn and Harvick was sliding up from below to get into line, Instead, he clipped the left rear of Hamlin's car, sending it spinning and into the wall. Dale Earnhardt Jr. also got collected and suffered significant damage, eventually returning to the race about 150 laps off the leaders.
"I just wish I had some kind of car left so I could show him the favor back," Hamlin said of Harvick.
NASCAR modified its rule about drivers exiting their cars after Kevin Ward Jr. was killed during a sprint car race in New York after being struck by a car driven by Tony Stewart. The new rule bars drivers from approaching the track or moving cars after an incident.
"I'm just frustrated because we had a good run going," Hamlin said. "I thought for sure after the first couple runs that we were going to win the race."
Harvick, meantime, radioed Hamlin's team apologizing and accepting blame for the incident.
It was unclear whether Hamlin would face a penalty for throwing equipment onto the track.
It was the second year in a row they have tangled at Bristol. Last August, the two were among several caught up in an accident, and they had a confrontation following the race, but came to a peaceful understanding.