I'd go with a Glock, any Glock as long as it's a 223AI. Mount a 6x MQ fixed fuhquer on it and you'll have everything covered. Google it.
Yep,
But you forgot to advise him to run good boolits only. I'd recommend a hard cast Keith, about 65 gr or so in that AI. Nickel plated brass too.
And he better get a 7 twist tube for it.
Geno