Try using the search feature on this site to access numerous threads dealing with the 835 and choke combinations.

I have a ported Star Dot .676 on my 24" barrel 835 and I shoot the 3.5", 2.25 oz Nitro 4X5X7s. I get 246 hits in a 10" circle at 40 yards.

My dad doesn't bother with a lot of patterning. He uses the Ultimag or whatever the name of the stock extra full Mossberg choke that came with the gun and uses 3.5" lead turkey loads (I don't know which brand or shot size). He kills turkeys with it, but note that he missed one last year at about 40 yards. I don't know why and I'm not blaming it on the loads or choke, just pointing out all I know.

If you want the ultimate combo for the Mossberg by a Primos Jellyhead or Rino extended choke and pony up for some of the loads from the Nitro Company, specifically load #H51013M.

http://www.nitrocompany.com/