You have peaked my interest why you would want a rifled choke for a 20 ga. They do virtually nothing to enhance accuracy in a 12, what's the advantage in a 20?
I don't want it... a family friend does, he thinks it will help with sabots because he can't buy a rifled barrel. I did find a choke, dealer out Ottawa way.
Buffalo's Outdoors did show a pretty good case for the rifled choke with standard rifled slugs:
https://www.youtube.com/watch?v=PzWKjhWyxpw
That being said, I played around with one and haven't seen benefit yet. Distance was only 20m and my red dot is pretty blunt (8MOA) so my test isn't really definitive either though. I am curious if the difference shows itself at longer ranges where stabilization may be improved (even if it can't stabilize a sabot slug properly).



























