What fabs says is correct....actually approx 21 inches for most loads. The only real things that happen because of the porting is..one.. There will be a great increase in the perceived report of the gun. Meaning it will be a LOT louder to those near you. Even for yourself. two.. There is a small reduction in the amount of barrel rise...mostly noticeable between shots when you are firing quickly. You will probably be able to acquire the target a little quicker. In the real world of waterfowl hunting....will this make a real difference?? The answer is, of course,.....not really! Porting on a target shotgun like a skeet or doubles trap gun will help the more accomplised shooter a bit...but it takes a while to become an accomplished shotgun shooter. There is no real decrease in recoil. By the time the shot gets to the porting...the recoil level has already been determined. That is why those really neat looking ported chokes really aren't anything but another way to reduce the amount of money in your pocket
