I use an 870 with a 28" barrel as well and have never had a problem out to 45 yards with 2 3/4" shells. One is a tight modified (measures closer to improved modified) choke. It's an older gun and only chambered for 2 3/4" shells. When I used screw in chokes in my express (cheap 870 with matte finish), I still used 2 3/4" shells and 3" on occasion. The 2 3/4" turkey loads still performed just fine. I used the undertaker turkey (super full) choke and got excellent patterns with the federal turkey loads. The older ones with flight control wads worked great. For the op's shotgun, this is probably how I'd roll:
1. Super full turkey choke
2. Federal copper plated turkey loads: #4 or #5 shot with flight control wad.
3. Synthetic camo stock:
BTDT a time or 2..
Federal premium turkey load