While I cannot comment as to velocity changes for standard 12 ga bird loads, I did pick-up a fully rifled Hastings barrel for deer hunting with sabots in my BPS and it did reduce muzzle flip considerably and add a tremendous amount of noise. Since I wear ear protection and will be deer hunting alone, it fits my bill very nicely.
I wouldn't even consider bringing a ported gun into a blind for fear of having said gun rammed up my....well, lets put it this way...the ports would no longet be visible and I'd be walking on my tip-toes home.
