I've been raising and hunting the dogs I raise for a pretty long time. Someone posted the video below on this site a while back, and I have to admit had I seen this years ago I could have saved myself a lot of frustration. For the most part, I agree 100% with what this guy says.
My best advice for someone trying to get a dog to hunt deep is get a pup bred that way and just don't screw it up. Easy to shorten a dogs natural range...sometimes without even realizing what your doing.
https://www.youtube.com/watch?v=eGkdlpIxWbYThat is my video. Range can be bred in, but even then that doesnt make it automatic. I can take 10 dogs that I get at 4 months old and if they have never been messed with I can usually get 8 of them to go long 1000+ yds by 1 year old by themselves. Dogs naturally want to hunt, too often we mess them up