Everything needs to be bigger . The AR 10 is the platform that shoots larger cartridges like 308 . You ' ll have to buy almost everything new a . 308 lower receiver , a . 308 upper receiver , a new barrel , handguard , muzzle devicd . However , the lower parts kit , buffer , stock , and fire control group are compatible . Check out rar 10 for more information , and don ' t hesitate to ask questions . I built my AR 1015 after extensively reading and posting in these forums . The community is excellent , and since you ' re in CA , join us over at rCAGuns to figure out how to navigate these new laws . <| sep |> If you hate this sub so much , either stop complaining and do something , or leave . <| sep |> Behind the scenes footage of the last UK House of Lords session .