I'm away from home( so I'm unable to launch C2 and double-check myself), but if you'd like the turrets to point at a different ImagePoint then I think you may want to make your own turret. You can have a sprite rotate toward a location and set that location to the Sprite's ImagePoint X and Y.
For simplicities sake, you can give the sprite a LOS behavior and then, if it has LOS, Every X seconds it can spawn your bullet.
Another idea is to continue using the turret behavior and have the bullet rotate or set it's angle toward the ImagePoint that you're looking to be fired upon.
I think the best option is to design your own turret though.