I would do these steps
1st. Check to make sure the gas port/tube is installed correctly. If that doesnt solve the problem go to next....
2nd. Make sure you have the lightest buffer installed. If that doesnt solve the problem go to next....
3rd. Drill out the gas port... For this Google "300 AAC Blackout gas port size"
"When seconds count the police are minutes away" (Original Author Unknown)
"I am not nor am I affiliated with Palmetto State Armory"