ED... thanks for the tip... but I've been to thier website many times in my research
http://www.hr1871.com/Firearms/Shotguns/ultraSlug.aspx
yes they have rifled 12 gauges, but I have been unable to find any listings for 10 gauge rifled slug guns, as that would be an interesting & cost effective starting point for load & projectile developement ( I could also possibly machine a choke tube to fit either the Browning or Remington repeaters from a rifled barrel if I could find one...
... please understand, I'm not trying to out do what you have already done ( which is amaizing ), only trying to do something a little different... thanks again... MWM