If your bullet is sized properly for your gun,
and if the pressure is sufficient to obturate the bullet per the bullet hardness.
Is there a need for a gas check? Even at elevated velocities?
From what I have been reading, I suspect the answer is, or could be no.
Although I also suspect powder burn rates may play a role in determining whether a GC is needed. Maybe it is simpler to use a GC and not worry with all the variables.
Please help me understand.