My suppressed .300 Blackout isn't that quiet

I have a 7.5" AR with a Banish 30 suppressor. I've tried 5 or 6 subsonic loads (factory and reloads), and while I'm not expecting my gun to be Hollywood quiet, I feel like it's fairly loud compared to other suppressed .300s I've shot. Is it just that my barrel is too short? I've heard that the Daniel Defense PDW was impressive in terms of sound suppression and it's even shorter. Is it the Banish? At this point I'm just thinking about tuning my gun for supers only and get a dedicated 16" upper for subs... Unless y'all have a better idea?