RE: Mossberg 835
Yes it is long enough....some would say a perfect size for a turkey gun.
If you are planning on shooting heavier than lead loads you will need a new choke tube since the factory one is not rated for it. If you are shooting lead you will be fine. I have gotten excellent results with an Indian Creek, and Hevi-13 3" 2oz #6, or Hevi-13 3.5" 2.25oz #6.
I posted this same reply in the guns forum.