I would suggest, right now, if you haven't already, get him a good 17 HMR rimfire with a decent scope. Have him practice a lot and shoot varmints,etc. sniping squirrels, etc will really help develop his skill set. Aim small, miss small works just as well for a 50yd squirrel as a 300yd pronghorn! It will also work swell in a prairie dog town if you can swing a trip in early summer. the great thing about prairie dogs and antelope is the boy "will see a lot of animals"! That is so very important for a youngster. We old guys sit around and day dream and we can sit on a ridge all day ( well, a big part of the day!) but a kid "needs" action. Good luck to you pard!