man, that sounds lika fun investigation !!!!

i've never seen a .223 handi that wud'nt shoot store bought ammo at least 2" @ 100yrds.
with all attachments in order and fitting is in proper spec.
your eyes can fool you when look'n at the crown.... tell him to take a q-tip and insert in the crown area twisting in the same direction as the rifling, if ya come up with some cotton pulled loose or fraid.
you might need to do a "crown touch-up" located in the (FAQ'S).
1:9 and 1:12 should handle the 55gr ammo. i know every one i have, had, held, shot, borrowed, stole
or seen have without major complaints. even with the cheap offerings out there.
don't give up !!! ifin the barrel is good, it can shoot.........

it had'nt been shimmed

has it ?
if this is a new gun, send it back. if its old, ask him if it has ever shot decent.
gotta bore scope ?? that might be inline for him to check too.
good luck.......BTW----my avatar speaks for itself
