Note that the above are just parts, and of themselves, are not controlled. HOWEVER, if you also own/possess an AR15, things are a bit different.
You aren't going to get busted for a short barrel assembly, which requires tools to install, but you COULD if you had a complete upper with that short barrel installed, because this can be installed on your AR15 in seconds with no tools. You could be charged with "intent to manufacture an NFA weapon", etc. "Intent" could, theoretically, apply to the M16 parts as well, though that's a bit less clear. Clearly, though, BATF doesn't want you to have them along with an AR15.
-Troy