First off, you need to give us some details on what you have here. What manufacturer, how many rounds through it, what accessories come with it, etc.
I think the reason for the post above is that it appears to have a 14.5 inch barrel on it. If it has a permanately attached Phantom flash hider on it then this would be ok as it makes it the legal 16.1 inches needed. If not it would need to be registered as an SBR to be in this configuration.
Secondly, you had this posted in the Want To Sell section of the board. When posting there you need to have a price listed. This is the place for questions and I / we will be happy to try to help given the needed info.
Nice rifle, now lets see if we can help you with selling it.