This might be a dumb question so at a minimum I hope I can ask the question in a way that is understood. 
If I were to make a SBR from an AR15, is the SBR still considered an “assault rifle” or does it fall under a different classification because it is now an NFA registered firearm or doesn’t it matter?

If I were to make a SBR from an AR15, is the SBR still considered an “assault rifle” or does it fall under a different classification because it is now an NFA registered firearm or doesn’t it matter?