Can only remember a few details...
MC is teen male (I think) who is given parts in movies as a stunt double for a high profile actor IIRC involving scenes such as precision high speed driving, flipping a car, sword fights etc. At some point he transitions to become the lead himself (dont remember why). I also remember a scene where some terrorists had taken offense at something he had said in an interview or something and decided to take revenge by throwing a grenade at him. He notices the incoming grenade, catches it and immediately throws it right back. The attack and his immediate response is all caught on film and the terrorists' parent organization basically declares war on him.
Any help identifying this story would be most appreciated.