I'm saying that a SEAL shooting a suppressed SMG feels nothing after dumping magazine after magazine downrange. There's no way this is causing concussions.
Grandpa's 30-06 will rattle your fillings a little bit after one round - still probably doesn't result in TBI.
SCAR-H, M14 EBR, M249 SAWs and M240 all shoot 7.52mm x 51mm NATO (compatible with .308 but slightly different chamber pressures)
As I said, we don't if calibers below .50 cause significant damage when shooting in excessive amounts. Trying to figure it as a layman is useless. It's better to show epistemic humility than try to assert one way or another.