11-87 barrels will fit and work on the 1100 G3 action. There may be low-bolt-velocity functional problems, as the orifices (for 26” & 28” field-grade vent rib barrels) on the 11-87 are smaller than those on the corresponding 1100 G3 barrels. This would be more prevalent using target ammunition. The same may be true for non-compensated barrels (Trap, Skeet, Deer), but I doubt this usage would be as likely to cause functional problems as the orifices are sized to provide robust performance over a narrow range of ammunition.
1100 G3 barrels will also fit and work on the 11-87 action. It’s possible that the 11-87 action will run faster with a G3 barrel, which could be a problem (function & endurance life) when using 3” magnum ammunition.
