Is there a Double barrel simi automatic shotgun?

Answer 1

no there isn't. the double-barrel design was intended to provide a second charge to a breach loading gun without reloading. It was useful for hunting game-fowl; if you miss with the first shot, you can get a second shot off before the bird disappears into the brush. For any shotgun with a more sophisticated ammunition loading system, dual barrels would add nothing of value, and reduce the gun's accuracy (since the force from the shot is off-center, introducing a slight torque).