Got my son a Ruger compact .243 when he was 8. Great little gun. I wouldn't worry about buying a "duplicate", get him what he needs to use. The other option would be a Rem Model 7 with the youth stock. Once he gets older, you can get a full size stock for it and he's good to go. My son is 14 now and still uses his compact, he loves it - even though its actually kinda small for him now. My choice would be .243 or 7mm-08. Have fun