In my experience, a turret firing a bullet sprite will create that sprite at whatever the angle the turret is facing.
Predictive aim with the same speed as the bullet sprite's bullet.speed will therefore rotate the turret to be pointing in front of a target.
Thus, when a bullet sprite is created, its angle is pointing to where the target will be when it travels there and collide moments later. I don't have a problem with angles and what not.
Do you just spawn the sprite with bullet behavior On Shoot, or you add a angle correction following spawning the sprite as well?