I'm going through the exact same thing myself, only with a 24 yr. old college graduate now living & working about 2 hours from home. He's got a good job as a Mechanical Engineer, and when he visits he still goes with me to the range to get some smoke on his face. He has all of his own equipment, but no desire to shoot & clean it in an apartment setting. His rifles & shotgun are hanging up on a gun rack in his dining room. One of these days I'm going to take him shooting near his apartment and come back to his place and show him how to clean his gun again. Maybe that will do it?
I am really blessed that we developed such a bond through the shooting sports. I won't "push" him either. New car, girlfriend there with him (no ring yet, but it's coming), etc., so he has a lot of distractions. I remember when I was his age. All I wanted was, well, you KNOW, lol, so I can't complain much.
May we both continue to be blessed with our son's time & attention.
Dave