A friend of mine has a 9 year old son who shoots with him. His son currently uses a .22LR rifle (sorry, forgot to ask which one, it is a semi though), but he feels it is time to move him up to something else. What would be good for a 9 year old who is very well aquainted with his gun? I thought berhaps .17HMR? Any others who have better insight into this situation? Any help is appreciated.