Most crimes are not commited with legally registered guns, criminals use weapons that are illegally obtained so they are harder to trace. Even if you could confiscate and destroy every privatly owned gun in the country, there will always be someone willing to make a lot of money illegally importing them. If you don't think that is true, look at prohibition and drugs. During prohibition, alcohol was illegal. Instead of getting rid of alcohol, the law helped organized crime to gain strength.
Drugs are illegal now.
Instead of stopping drug use, the gangs are getting stronger and larger every day. You can even look at countries with strict gun control. Look at England,they have very strict gun control, but the criminals still manage to bring them into the country. There are several countries that have strict gun control, and I don't know a lot about most of them. I did, however, live in one of them for about a year an a half.