I have a 870 Remington Express 12 gauge, first year offered if I remember correctly, in the 21" barrel with the Remchoke system. All I have ever fired through it were Foster-style slugs since it's a smoothbore barrel. I tried IC and Mod chokes with Remington 2/34" Slugger loads with it, both shot pretty well, no discernable difference at 50-100 yards. They plopped in with deer-of-ribcage accuracy. If you're looking for hunting accuracy, run a variety through it,to see what it prefers (painful as that sounds). Federal Tru-balls did well also, Winchester it was picky about.