That's impossible to say. But the private sales would all be used guns. Most of the NICS numbers should be new guns, right? Adding more to our collective arsenals of freedom :-)
Another way to look at it is that that's 4.7 million more guns shooting up ammo that I can't get my hands on!
Well you have to take away the used guns sold by a FFL dealer, but it's still a boatload of firearms!