Unless you just want a new gun, the 870 is plenty. Its what I use.

I see alot of guys buy 3.5" but never bother to pattern it. I would rather have a good patterned gun than a 3.5" right out of box.

I use a .22 mag only leave one hole they dont run over 10 yards. It give me a longer shot dont have to be so close to have a turkey dinner

at 40 yds or less its not really going to matter,shot size will pattern different, one of my favorite turkey guns is my NEF 24'' 12 ga. single barrel. problem is it kicks like a mule, but 40 or less hes had a bad day.