The net effect is already known. We have jurisdictions with strict gun control in the US, and there's no causative decrease in armed crime. Gun control, at best, hopes to effect the supply, the supply is already massive so it can't do much there, at worst it's an attempt to control ownership which no law can accomplish: laws can only regulate legal commerce. Black markets just pop up and go around fhem when there is massive demand, and with the already massive supply prices stay relatively low. Example: the so called drug war. No impact on supply or demand. And with vigorous gun laws, you will create a black market.
So if you want to reduce supply, you have to get rid of guns: confiscation or buy back with significant incentives, and even then you can't eliminate supply. But thats what youd have to do. And to reduce demand you have to both reduce crime, and increase penalties on gun crimes to something so severe you both deter and slowly eliminate law breakers.
If you're serious about reducing gun violence, look at the root cause of most of it: drug control laws. Get rid of drug prohibition and a large percentage of all violent crime goes away. Anything else, including gun control laws, is only going to make a minor difference, at best, and is likely to just make things worse. You have to eliminate the root cause of violence, the gun is not the cause, it's just one means, and don't kid yourself if a lot of money is available to a criminal element, they will get all the guns they want no matter what laws you pass.