Gunsmith without a doubt. If you have to ask if your not doing something right with something basic, you probably don't want to "tinker" with it. Trust a professional and be SURE. It is the most important function on a hunting rifle. I don't mean to sound arrogant as I'm not a gunsmith, this is what I would advise myself in this situation. Hope it is a simple problem, and you have good success.

kd.