Its usually not recommended to shoot steel through a fixed choke. I personally do not recommend it.
However, my father regularly shot steel out of his shotgun that has a fixed full choke and he never had any issues with wear, bulges, cracks, splits etc. Patterning maybe wasnt the best, but it killed and killed often, with no consequence to the gun.
So to answer your question, you can fire anything through any gun....but if what you're firing is not recommended, then you will damage the gun. I would proceed on the side of caution and say no, only shoot lead from a fixed choke gun