Big Ears
Member
If you need to go heavier than 243 think 6.5x55, light on recoil and strong in down range effect. 140gr travelling at 2700fps has the knock down power of a 165gr 308 at 300yds. This is a really underrated calibreI would start with .243, plenty for ‘Lope and deer, very low recoil. I know OP referenced light rifles, but for youth 7mm08 can be a little "kicky" in a superlight compact.
If that's the case you can add weight to the forearm and stock pretty easy on Ruger American to moderate recoil if needed - several YouTube videos show how.