I would also endorse the point centrarchid makes and say free ranging may not be your best option. I lose chickens to predators every year. For some this may not be acceptable.I would prefer to avoid a competition that I would probably lose. Best to seek advice from a wide range and do what "makes sense" and is within my context/ability. Please note my last reply to shadrach. Free range makes perfect sense to me.
My caution is due to the abundance of predators in my area (very rural with few permanent residents). I do have a neighbour who opens their coop door through the summer, I intend to ask their experience with free range and bird loss as a result.
A lot will depend on what you want your chickens for and the type of predators you have.