I'm with ya, that's why I was curious as to where this project was at. I think a KSG shooting slugs at 200 yards accurately would be bad azz!or I might wind up with something better that others will want. Really doesn't matter it's my wallet and my desire. If I wanted the standard ,I never would have taken up custom guns as an obsession. It's not a sin to take a street sweeper and turn it into a snipers dream. That's what spare barrels are all about.
Do rifled chokes really work? I always wondered if they improved accuracy with slugs.The Kel-Tec is really not a great choice for an accuracy slug gun, but would work.
Having a barrel attachment rifled is going to be very expensive and it would be hard to find someone to do it.
I suspect a better option if you must have a rifled Kel-Tec would be to install a muzzle attachment that uses interchangeable chokes and buy a rifled choke for that.
I'd think you'd get the same or better results by buying as many brands and types of shotgun slugs that you can get and test firing until you find the one brand/type that shoots the best in your specific gun.