Ohh No this is gonna start something I can already tell. As far as I have been able to tell with shooting 3 and 3.5 is that it will increase your limit by about 10 or so yards. My 3" will kill a turkey cleanly out to 50 yards and I dont think I would ever shoot any farther than that even with a 3.5. Another benifit is that a 3.5 has many more pellets which will benifit you at ranges longer than 25 or so yards. Anything less than 25 yards with a 3 or 3.5 you will about knock the turkeys head off. The ONLY way to tell your guns limit and ability is to go to the range and shoot some shells. Start at 20 if it looks good move to 30 then 40 and so on till you aren't getting at least 15 pellets in the bone area of the neck and head. Good luck.

On another note if you shoot 3.5 make sure your gun has a little weight to it I shot a very light 12 gauge with a 3.5 and it kicked so bad it made my nose bleed. Although I have had some 3 inch shells kick alot worse than the 3.5. Just don't overdo it at the range.