Having a very similar debate for my 7 year old right now.
I have Grendel and 6.5C setups but think I’m just going to allow him to use a short (16”) barreled AR 6.5C that is using 120ish bullets at bottom loads. Should be able to push 120’s about 2750 or so.
The ballistics on that nearly match full power 6C loads out to 500yds or so(BCs are close) ….saves me from having to load a new caliber, build a new gun (although I want an excuse), and AR setups really help with shorter LOPs for kiddos.
I have Grendel and 6.5C setups but think I’m just going to allow him to use a short (16”) barreled AR 6.5C that is using 120ish bullets at bottom loads. Should be able to push 120’s about 2750 or so.
The ballistics on that nearly match full power 6C loads out to 500yds or so(BCs are close) ….saves me from having to load a new caliber, build a new gun (although I want an excuse), and AR setups really help with shorter LOPs for kiddos.