Based on experience IMO, you should not have any trouble shooting steel in a 311, especially with those open chokes. Just don't go over about 1450 fps.
I myself would shoot 1 1/8 oz loads. Don't forget 1 1/8 oz of steel will give probably the same amount of pellets as a 1 1/4 oz lead load and the 1 1/8 oz load will probably be 1300 fps or faster. Steel will also pattern a little tighter than lead.

Last edited by 2holer; 12/19/12 08:44 PM.