I actually got the same figure from a S&W rep. It has nothing to do with union rules; it's simply an infrastructure limitation.
300,000,000/300/365= 2740 years until the gun shortage is over!
But good news, toss in Ruger's larger contribution and the timespan drops to 249 years until everyone in the country has a gun and the panic is over
(our population's gotten large enough that we get to have fun with our own "Marching Chinamen" scenarios