Hi,
When using steel shot, you should only use stainless steel choke tubes with modified or more open chokes. You should not use steel shot with Extra Full, Full, or Improved Modified Chokes of any kind. If it is a fixed choke barrel, we do not recommend using steel shot, as it may damage your barrel. Cheers.

Edward, there are a few misconceptions out. Steel Shot through #4 is fine in Full Chokes. Since steel shot does not compress, anything larger should not be fired through a full choke. This is about the best read on Steel and Chokes I have found : - fieldandstream.com/blogs/the-gun-nuts/shooting-a-full-choke-and-steel/