Never had a hickup from my supermag 870s feeding 2 3/4. I try to alternate their uses and the Express supermag gets used abunch on squirrel/grouse/skeet and it eats up alot of 2 3/4 shells. ifone has feeding problems with them it may be a defect in the gun.
ORIGINAL: legion
From what I understand, the 870 Express will shoot 2 3/4" and 3" shells, while the 870 Supermagnum will shoot 3 1/2" and 3" shells (they say it will shoot 2 3/4" shells, but I've heard they jam on the Supermagnum).