It is actually quite interesting. In the FRT notes section it states that the 416 is "similar" to the M16 (uppers interchange), and that the MR223 is the civilian version. However, in the law reference used to assign class, it states that the reason it is restricted is because of barrel length only. Based on that, one could install a 471mm+ barrel and it should be classed as NR.
Not quite. It is my understading (after speaking with multiple poeple at the CFC) that once a receiver is regsitered as restricted.. it can NEVER be re-registered as non restricted. A perfect example is the Ruger Charger...