I would caution AGAINST using steel. If you are hunting where non-toxic shot is required, I'd use HeviShot or bismuth or tungsten, but not steel. Steel doesn't have the mass (weight) per pellet and hence lacks (per pellet) penetration power. I'm not saying steel shot "bounces off" turkeys like bullets do off Superman, but I'd think using steel would increase the risk of a wounded, not dead, bird, especially at longer distances.

BUT, most "lead only" chokes DON'T WORK with the other non-toxics, (HeviShot, bismuth, tungsten) either. (BUT/AND shooting an improved cylinder or a modified choke will usually give you a tighter pattern with non-toxics, equivalent to a lead full, anyway.)