Before I determined that I had a problem, I would use the BSS first with the ammunition I use on pheasants. At the minimum pattern the gun.
Have you actually measured the constrictions with a professional bore gauge to determine actual choke? Not the brass things that you stick in the bore.
After I had done those things, I would make a decision.
And then If I determined that the chokes were too tight, I would not install tubes but only change to IC/Mod.-Dick
Further to what Dick said, if you still find it patterns too tight, you can also consider spreader shells like Polywads or spreader inserts if you reload.
I have a gun marked IC/Mod but that shoots tighter. I reload using Polywad Spread-R discs.
