What exactly are you trying to make happen? Do you want a bullet that flies straight but looks like it's "spinning" or do you want the bullet to actually curve through the air?
Typically, if you want something to appear like it's spinning, you're better off making an animation sequence for your object so it's "spinning" via animation - then you can just shoot it like a bullet in a straight line. If you want it the curve through the air, you're better off just adjusting the angle of the object using events (like every tick, bullet.angle=bullet.angle+0.1)
Hope this helps