I bet you have a 835 or 935 Mossberg
Yes a steel shot tube will work .
BUT Hevi shot patterns so tight that I would not recomend them.
I recomend that you go no tighter than the MOD .
Pattern that tube and I bet you will like the results .
I use a Rem 870 and only shoot a Mod for pass shooting and it is to tight if I was to shoot decoying birds.

Even with Hevi shot ,Please be ethical no HAIL MARRY shooting , try and use 60 yds as a max.

From your Member details you are 100 years old , think you need to update it ??