Hey AS, long time no see... I know internals very well, while on the topic of externals, that's a different story. Now, I would like some assistance and advice remove my Krytac barrel nut. My questions are as follows: -Is this really the barrel nut? -How would I install a Madbull DD 12" Lite RIS on my beauty? -What tools would I need to install the rail? What I have already done: -Removed the Defiance rail system -Removed the gas tube/gas block Picture: http://imgur.com/j10l4jj Any help is appreciated, thanks!