I'am starting to get into this multi-gun stuff and I am also starting on building a open shotgun but before I go any further I'am a tool and die machinest so it is not a problem for me to get the work done, Ok now I'am wondering if anyone has knowladge on porting shotgun barrels ? Is the #of ports important or size or placement ? I know a little about shot gun barrels like the first 18 inches the powder burns out and how ever long the barrel is after that is just drag and if you have chokes in your barrel you want to place your ports behind the chokes, so the big question is what size how many ,and where, and maybe what pattern?? THANKS