You seem to have missed the point. The gun laws already prohibit them from owning guns but they do it anyway and commit crimes. No additional gun laws will suddenly make criminals obey the law.
But somehow gun laws work in every other civilised country... Odd.
Well if you are sure it's not the gun laws then instead fix the other laws which are putting people in poverty and creating the gangs.
So your solution to people breaking the law is to create more laws that they won't obey? The United States is fairly unique with their bill of rights. Codifying the right to bear arms, which in the view of the founders would allow the citizens to rise up against the government. This is well documented in their own writings. We currently have far too many restrictions on what citizens are allowed to own.
Oh sorry, my bad. It actually sounds like you want to legalize crime.