What are critical commons points of a turkey gun in the 12 guage? -OR- at least explain what is your preferences or showstoppers for you forking out hundreds of dollars for a turkey gun?
SITES- Fiber optic open sights. I am a big fan of having something on your turkey gun. It's too easy to forget to have your head in the perfect position and open sights give you a clear reminder. I'm sure that scopes, red dots, etc work fine, but I don't see any improvement that they make to justify the extra weight, complication and cost. Calling a turkey into range is hard. Shooting one is easy - it's a stationary target at 50 yards or less with a shotgun.
BARREL LENGTH- I used a 28" barrel at first. I switched to a 20" and love it. So much easier to carry in the woods. Velocity loss is negligable. Patterning loss is a myth as far as I'm concerned until someone shows me some data to the contrary.
ACTION (single, double, pump, auto)- I use a pump but a single shot would work fine.
CAPACITY- Can't be more than 2 in the mag and one in the chamber in CA.
CHAMBER (2 3/4,3, 3 1/2)- 12 ga 3" chamber allows me to shoot 2oz of lead shot. That's plenty. If you can't get them close enough to kill them with that, you need to change your hunting tactics so you can. No matter what you shoot there's always going to be some turkey that hangs up too far away.
WEIGHT- As little as possible. My current Mossberg is 7 lbs. That's plenty.
MANUVERABILITY- See above.
RELIABILITY- Not a problem.
CAMO- Not required, but nice to have.
Sling swivels are a must.