If he just wants something to practice with he only needs a .22 but hey, there's nothing wrong with wanting. If he's accurate on out to 200 yards with a .22 then he'll be deadly with the M16.
Outstanding post! When people ask which car to get among a Porsche, Corvette, or Ferrari, I always point them towards a chevy cavalier or used ford pinto. Afterall they are all cars and do the same thing.[8D]
Seriously, I would consider a Rock River Arms mainly because they use milspec buffers and offer a high quality product at a relatively good price.