I was bored this-morning so I was doing some reading about the history of the AR-15. This led me to the wikipedia page that talks about adding a forward pistol grip to an AR-15 designated as a pistol constitutes manufacture of an AOW and has to be registered.

So, my question.... I have a stock 16.1" barrel LE6920 and may or may not have a Magpul Vertical Grip mounted to the handguard. How I interpret the law is that it would be illegal if the barrel is less than 16" because the rifle would be considered a pistol. But, since the barrel is 16.1", this is legal...(?)

I get the feeling that it's insignificant, but still want to make sure I understand the law properly.