RE: What is the best turkey shell for a Mossberg 835
Hard to say - every gun and choke seems to be different.
My 835 with a Star Dot .690 tube shot the Winchester 3.5 inch, 2.25 oz of #5 like crap. Federal Tightwads (2 oz #6) didn't shoot much better. Ported chokes supposedly defeat the purpose of the Federal Tightwad anyway because they tend to strip the wad from the shot. Federal tightwad rounds shot better with my unported Mossberg UltiMag turkey choke.
The round that shot the best by a very large margin from my 835 was the Hevi Shot, 1.75 oz of #6. Devestating number of hits in the head and neck from 35 yards. No comparison to the lead shells.