A local shop had a Carlsons rifled choke for my 20 gauge 870. I've never even seen a rifled choke before so I had to try it.
Lee 575 round ball @ 30 meters, my usual "Economy Slug Load" which means a factory trap shell, just cut the crimp out,remove the shot and roll with a slug. Rio 24 g (7/8oz) shell this time.
Five balls in the target. No bags, elbow resting on an icy,wet table. Red dot.
.
I use a thick 28 gauge fiber wad under the balls. Will test further, this might work 50-60 meters but now I wanted to save the rest of the slugs in my pocket. Sort of exciting to actually hit the target sometimes.
I also tried Svarog pellet slug,no remarkable difference compared to I/C choke.