First of all let's assume that you are right that fewer guns would make it 
in to the country, that sounds great (to those that see guns as inherently
evil) except then every one  of those guns would be in the hands  of someone
who obviously couldn't care less about following the law, after all they 
got the gun illegally, so is more likely to commit a crime with that gun.
Great then everyone with a gun is likely to use it in a crime, nice system.

Now  as to reducing the number of guns  coming into society by making it 
illegal to manufacture, sell, or import them in this coutry,  let me use
a parallel for empiric evidence.  The amount of cocaine in this country is
far less since its manufacture, sale, and importation was out lawwed.    If
that last statement is true then perhaps we should consider your plan.  This 
could also apply to drugs in general.