3.5 in turkey loads, you need near elephant gun recoil to shoot a bird. Who need shoulders?I have a couple of shotguns that shoot 3.5" shells, but never used anything other than the Browning Citori O/U with 2 3/4" pheasant loads using #5 shot. Never had to use the bottom barrel.
The .410 is going to be a challenge getting them in close enough to be effective.
Have you patterned it yet?