That might be something you'd have to test yourself. Typically, turkey hunting involved the tightest chokes out there, so a cylinder choke is clearly not ideal.
Turkey hunters usually aim for the head/neck of a turkey, which isn't a big target. Some people check turkey hunting patterns by shooting a 12" target. If approximately .6 ounces of shot are hitting the target (about a third of the pellets from a 1-3/4 oz. load), that's maybe close to your maximum range. That might mean 40 yards in some guns. I'd suspect--and this is just a guess really--that you'd have to be closer to 20 yards to put that much shot on target. Not to say you couldn't kill one from farther away, but it might not be as clean as it would be will a more optimal setup.
EDIT: I wrote this before I saw Dave's comments. sorry for the redundancies.