The DAG training bolt carrier has a reduced diameter bolt head which mates up with the reduced diameter case head of the blue training ammo...this is a safety feature so that regular ammo (this also includes blanks) cannot be used. This is why you were not getting any primer strikes with the DAG training bolt carrier / blank combination. The DAG training bolt carrier has no provision for lockup...so firing regular ammo (or even blank ammo with BFA) would be extremely harsh to destructive to catastrophic for the weapon.
Having said that...my experience with plastic blanks with standard bolt carrier and BFA has been mixed. The fluted chamber allows gas to flow back over the plastic case and tends to melt and collapse the plastic case and gum up the chamber after a mag or so. I haven't tried brass blanks myself, but I would suspect they'd do much better in a fluted chamber gun vs the plastic blanks.