Id measure the length and number coils on the spring. You can only use carbine buffer spring in carbine buffer tube and only rifle length spring in rifle length buffer tube. If you have the correct length spring and buffer the next thing to check is the size of the gas port hole. You didnt mention the manufacturer of the barrel but undersized gas ports have slipped out with several manufacturers. The size have seen reported for 6.5 Grendel 20 barrel is .0935 (same size as 5.56/223). If the port is smaller than this youll probably need to drill out the port.
If the port is much larger than .0935 you are probably over gassed and getting bolt bounce. I bet the gas port is undersized if the gas block is centered over the port. Ballistic Advantage has a habit of shipping 6.5 Grendel barrels with small gas ports.
I copied this but this should match up to your spring.
While most rifle and carbine springs have exactly the same diameter, they come in different lengths. ... A standard carbine spring will measure about 10.5 and have 37 to 39 coils, but a standard rifle spring has a typical length of 12.75 and boasts 41 to 42 coils.
If the port is much larger than .0935 you are probably over gassed and getting bolt bounce. I bet the gas port is undersized if the gas block is centered over the port. Ballistic Advantage has a habit of shipping 6.5 Grendel barrels with small gas ports.
I copied this but this should match up to your spring.
While most rifle and carbine springs have exactly the same diameter, they come in different lengths. ... A standard carbine spring will measure about 10.5 and have 37 to 39 coils, but a standard rifle spring has a typical length of 12.75 and boasts 41 to 42 coils.