Mine are free ranged all day and never leave the yard. We have 28 acs and its suite a distance for them to travel to reach the neighbors but they never go more than 100yrds (absolutely max) from the coop. Most of the time they are within 60 yrds.See if this will help. In my experience, the more you let them out, the farther they roam. They get comfortable with it. I am hoping you do have a run, but if mine wander too far, I quit letting them out all day, I don't let mine out at the same time each day, as that also helps with predators.
But I find, that if I have to keep the enclosed for a while, when I let them back out, they don't go as far. Or if I limit the time they are out, helps too.
Monica
I know thats still a lot of ground on a 3ac parcel. I would suggest looking into adding 4"x4" (assuming your chickens are not small enough to fit through) woven wire fencing to the existing barbed fire fence. It may be just enough of a barrier to deter them from wanting to walk around it and keep them from your neighbors.