Quoted:
It is my opinion and the opinion of people much smarter than me (and backed with science) that porting is worthless on a shotgun. Shotguns are just too low pressure to have porting as typically seen work, just look to how big the ports have to be on a 9mm or .38 super race gun, now consider they are working with much higher pressures and shorter barrels that can use that pressure. By the time the projectile reaches the ports on a shotgun and adding to the fact they start with very low pressure in the first place, there just isn't the pressure needed to make a difference. 7M3 will back me up, even if it is just because Browning uses porting on their sport guns and if they do it, it must be wrong.