We prohibit the sale of alcohol and cigarettes to minors yet they manage to get those things with little to no trouble. We prohibit the manufacture, sale and possession of certain drugs to everyone yet we have a multi-billion dollar illicit drug trade in this country. It's no different with guns. No matter how illegal you make them they will still be on the streets and criminals will still have them.
Would you really feel better if all law abiding citizens were disarmed and only the drug cartels and homicidal maniacs had guns?