I'll pass on a bunch of "I heard" stuff, other than to say that there seems to be no particular ballistic advantage to shotgun barrels longer than around 20".
The main deal with barrel lengths is balance and the rate of swing on flying birds. Faster handling via shorter barrels (26", for instance) for quail; longer for doves and waterfowl.
So, for a turkey gun, it sems to me that the tight chokes now available are more important than barrel length. Shorter barrels would make for easier handling in thick cover or inside a box-blind.
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