If you can take a dime and be able to fit it into the end of your barrel, then its not a full choke. Get what am saying?

If your hands are to big, get some pliers, get a good grip on the dime so it does not fall down into your barrel. If you can stick the dime into the in of your barrel, the end that the shot comes out, then your good to shoot slugs, maybe.

Now on your barrel does it say anything? Does it say (P) or proof Steel? If it says (P) its proof and I would not feel safe shooting steel shot out of it. Foster type slugs are questionable, "Lead" Buckshot and "lead" birdshot ONLY, they will do OK.
If it says proof steel then you can shoot steel shot out of it without to many worries. But if it is a fixed choke like it sounds, and its a full choke. I don't care if it says proof steel or not. You start shooting BBB out of it or any of them goose or turkey loads out of it, your gonna split that barrel right in two sooner or later.

I may not be very old but I've been around guns many years, know my stuff, seen what happens when full chokes blow with heavy loads and have seen many other shotgun problems.
Others will tell you some stuff on this, this is just my 2 cents worth.