Guns have to be manufactured somewhere - but that does not have to be from a manufacturer inside the US under US government regulation, or from a business at all. Perhaps you are unaware of the illegal gun manufacturing in the Philippines? Perhaps you should download the recent documentary episode of Vice S01E01. It was on last week.
Guns aren't rocket science or nuclear weapons. Just as when Prohibition was implemented, if you banned making guns, people would just make them illegally. As long as there is profit to be made, someone will try to make it, even if they must risk breaking the law.
Even with guns made by licensed gun manufacturers, they are not selling them to criminals. They sell them to FFL dealers, who then make their sales. Those dealers are regulated and are supposed to only sell to legal individuals who pass background checks. Why should these citizens who legally purchase their firearms be targeted by government legislation INSTEAD of criminals who illegally obtain and use these tools? Use your head and think rationally and tell me how Feinstein's bill will lower crime statistics when it only targets legal sales? Criminals go to the black market because they can't go through the legal process of procuring a firearm. Is that too hard for you to understand? When these criminals commit a serious crime like murder, they overwhelmingly go for a handgun, instead of a rifle, so why are we only talking about legislation against assault style rifles?