it is. Nodak sold you a receiver for pistol or rifle use, by assembling it with a shorter barrel + still having a stock, you are "manufacturing" the short barrel rifle. If you bought it from them as a complete rifle, it would be different. Stupid as heck? sure, but it is still the way it is. What makes it even stupider is that the engraving goes on the lower, but its the upper that has the short barrel. How about the fact that on virtually everything except the AR15, it is the upper that is considered the receiver, not the lower..... None of what the ATF does has to make sense, it just is what it is.