All the above will get the job done, but a "turkey gun" is not needed. You can take your squirrel gun you have now, use a good high powered 2 3/4" or 3" shell,(same as you use to hunt squirrels) then learn to call the big tom in and wait till he get within a 35-40 yard range before pulling the trigger and you'll do just fine.
Aim for the neck where the feathers start .