I have a Mossberg 500 now with 18 1/2in barrel. It is only chambered for 3" shells though.
For the harder hitting 3 1/2" shells, I was leaning towards the Mossberg 535 "Turkey Thug" with ported choke.
"Turkey Thug"
Harumph! Hooey! Horsefeathers!
That's Marketing.
You don't need 10 guages or 3 1/2" UberwunderMagnumSuperDuper1Dollar-a-pop "Turkey Loads" to kill a turkey. The "deadliest load" I ever saw was a load of #8's out of a 40+ year old shotgun with a fixed modified choke- killed 3 birds with one shot when the guy only had 1 permit, which was only good for 1 bird back then......
This "3 1/2" Magnum" crap reminds me of all the "Buy Accuracy" rifle guys that think they can go out an buy a "sniper rifle" and be a sniper ...... How about learning to call the birds within 40 yards and killing them
with a load of 2 3/4" #6 to the head? .... If my 12 y.o. daughter can roll the fall boss hen at 30 yards with a 50 year old thirdhand 20 guage stoked with pheasant loads, why are you going to listen to some marketing campaign telling you you have to drop big bucks on special ammo/special gun /special cammo . etc?
What you need is a load and choke combination that doesn't have turkey head sized gaps in it at the range you are going to shoot.... and don't be so over optmistic about the range: you can't buy yards, just as the rifle guys can't buy accuracy.....
I have a theory ...... "people are more willing to spend money than time."
Patterning a flock , learning to call, even getting up earlier than the birds.... all that takes time ....... any idjit with more money than sense can amass enough money to buy a 10 guage 3 1/2" Super Duper TightTurkey Choked Wundergun....... It takes time and dedication to learn to hunt anything, incuding Turkeys .......