Oh yeah, 4V50 Gary's right too. I forgot Mitchell Arms also imported it as the M16 A1/22, and also the carbine version. But I don't remember what that one was called.
They retailed for between $275 and $300, and I think the carbine went for around $350. I have no idea what they would run now though.
Good luck finding one!
"Politics is supposed to be the second-oldest profession. I have come to realize that it bears a very close resemblance to the first."