here is a trick i was shown, seems to work. get a lead and fasten to your dogs collar. then go out and when your dog gets to that distance, hold it tight without warning. change directions without warning, each time letting the dog hit the end of the lead with his own force. act like nothing is up, or he will blame you. after a few times he should be paying closer attention to what you are doing and be less prone to range on you.
another thing i have always done is train the dogs to come straight to me when i whistle a certain way. always have a tasty treat when you do it, given when your dog reaches you. i start in my yard. when the dog is relaxed, i go to the other end of the yard and do the whistle, very loud. the dog should come fairly quick, when he does, give him his treat. keep up with this, doing it whenever. several times a day at least.
when in the field, it is really nice to have a whistle that will bring your dog in, no matter what.
thats my two cents. for what it is worth, that is why i dont like flushing breeds.