You need to add about $100 to that for most of them I am seeing. I don't know of any Aero Precision hand guards that are less that $140 or so. Average is about $189.
So with the cylinder in closed position can you hold back the release and get it to fire? If so then sounds like possibly the pin on the end of the release is broken (or worn) or the one in the end of the ejector rod is worn or missing not pushing the cylinder release back far enough?