To be honest I think that both Vang and SGT both either caught the train before it left the station, or actually built the train themselves! The
HD/Combat/Tactical/SHTF/whateverwecallitthatscatchytoday shotgun has only really taken off in the last five or so years. Hans and SGT were the first "big" names in that niche of Shotgun smithing. And the best thing about them, at least Hans, is that what he's doing today he's been doing since the beginning primarily backboring, lengthing forcing cones and porting.
Of all the barrel mods to make porting is actually the easiest to do. Brownells has a jig they sell ($285) that mounts on the barrel with the porting holes pre-spaced. Just drill and go. After you finish polish up the burls with a hone (they sell it too
).
I've thought about springing for it, but really can't justify it. But to be honest I'm not so sure that porting is
really nessecary. I've shot unported all my life so it would really have to impress me. Plus I'd have to port the barrels of all my guns, plus several others to feel like I broke even.
I'm sure a "general" gunsmith (BTW do they exist anymore?) could do a decent job of lengthing the forcing cone and back boring. Look in some of the hunting magazines for your area, or even the state wildlife commission guide books, often they have adds for "hunting gun" gunsmiths. Give them a call and see if they do. However all caveats apply, ask for and check references, request to see examples of his/her work etc.
Just my thoughts for what they're worth.