I do recall someone postiing their accuracy results with smoothbore mod choke slugs. Try a search for "slug"
I CAN tell you of my experience with Foster slugs and different chokes. However, it is for 2 different guns for the same slug, and it is for 16ga, not 12.
* Remington 16a Slugger rifled slug, 1600fps, 4/5 oz
*Custom Mossberg model 190,bolt action, rifle sights, 20" bbl smoothbore, cyl bore (no choke)
50yds: all on an 8x11" target, some touching, but mostly spread out. Best results from a COLD barrel.
100yds, some on the 8x11 target, but some not even found. Very "hit or miss" :roll:
Custom Winchester Model 12, pump action, rifle sights, 28" smoothbore, full choke opened to somewhere between imp. cyl and mod.
50 yds: 4holes touching , 1 1/2" grp, #5 about 2" off from that, total 3" or so.
100 yds: 1 1/2" low, 4" group.
For the Remington Slugger, some choke seems to work well. Note that on the box, mod choke is recommended.