Instead of focusing on the guns themselves, which there are too many of, a solution could be restricting the sale of bullets. Limiting bullets to those with hunting licenses for example, and giving it time, could reduce existing guns to useless pieces of metal, unless people make their own bullets?
Gun control has already worked quite effectively in the united states in many cases. It's impossible to say this decisively without a criteria, and that criteria ought to be realistic.
You do not examine legislation in the light of the benefits it will convey if properly administered, but in the light of the wrongs it would do and the harms it would cause is improperly administered.
Criminals usually wouldn't care if they were going to commit crime (like robbing a bank, for ex.) about breaking a separate crime, due to them being criminals, therefore making gun control only negatively affecting the upstanding citizens who want to stop crime by using guns. Gun control is useless.