I normally recommend 3" Winchester HV shells with 1.75 oz. of #6 lead shot to most folks who ask. That's a very good shell, that's widely available and very reasonably priced. It's probably been responsible for more turkey kills since its introduction in 1996 than any other turkey load.
I recently spent a couple of hours with the Winchester engineer who designed that shell. He shared with me some of the challenges that were faced in its development. We discussed the relative merits of #6 shot which I prefer and #5 shot which is the largest seller.
When I hunt turkeys, I use whatever shell I've been shooting the most of before the season. They all work.
"If he's out of range, it just means that he has another day and so do you."