I personally have looked at homicide rates of many countries, what their gun controls are, and if there was any difference after tightening or loosening the laws. My conclusion is gun control really doesn't have a effect one way or another. The UK the violent crime rate went up after the bans were enacted, in Canada rates continued downward on the same trend they have been on for decades.
Guns don't change someone's mindset, they aren't a drug. If someone wants to kill you, they want to kill you whether or not they own a gun or not.
I do believe in small controls such as requiring a licence (but it should never expire) that has a background check to verify you aren't a criminal, registering handguns and full autos (to prevent straw buying), but otherwise beyond that it really doesn't have much of a effect.
Up until 1978 we had looser firearms laws than the USA where we could still buy a full auto legally and it only be required to be registered. We never had the violence the States had. The answer isn't the fact that our laws were looser, rather we don't have the social-economic issues the USA has. Switzerland has some of the largest concentration of military rifles in the world, yet one of the lowest crime rates due to the fact the society doesn't have much poverty, drug abuse, and in general most people are very responsible/happy citizens.
One thing that is 100% verifiable is the tighter the gun control the more likely your country is going to turn into a dictatorship. I can't find a single example of a well armed populace that goes from democracy to dictatorship, but I can find plenty of examples that went from armed, to unarmed, to dictatorship. Easiest example in the last decade is in 2012 Venezuela banned firearm ownership, now they are a dictatorship where the people are starving and unable to receive aid because their country refuses to accept it.