How a criminal gets a weapon is besides the point. Whether or not they get one easily or not is besides the point.
If the question is whether guns or any sort of weapon is a good form of self-defense, it doesn't matter what the assailant has, but whether the rate of successful self-defense increases based on the availability of weapons to the defendant.
And all evidence seems to say that an increased availability of weapons for "self-defense" results in more homicides, more assaults, and less actual safety. Stand your ground laws in the U.S. resulted in an increased rate of homicides of 10% in states with those laws. States with lower gun ownership also have lower rates of homicide.
Of course, this then begs the question of whether it's an increase of guns causing more crime, or an increase of crime causing more people to buy guns, or some other factor that increases both. However, current evidence points towards an increase in guns creates an increase of crimes. As an example, women in states with more guns are almost 5 times more likely to be killed with a firearm than in states with less guns. Again, you can argue that more guns means a higher likelihood of being shot, but going even more precise, a woman is 6 times more likely to be shot by a person in a relationship with her, than a random stranger. A woman is 7 times more likely to be killed by her partner if her partner has a firearm. The availability of a firearm significantly increases the odds of being shot.
In addition, evidence also shows that ownership of weapons, particularly firearms, by victims has increased odds of the victim being seriously injured or killed. There's around a 400% chance increase in being shot during an assault if you carry a firearm for self-defense. There's around a 400% chance increase of being killed during an assault when you carry a firearm. Is it because people who are at greater risk carry firearms, or because you carry the firearm that you're at greater risk? Again, this requires more evidence, but it's highly likely that both play a factor. When an assailant perceives you as more threatening, they will either increase the severity of the attack to incapacitate you, or flee. And since firearms have a decent range, and the laws in America justify shooting somebody in the back if they attacked you as legitimate self-defense, the criminal has only one option if they discover a gun on their victim. They have to subdue the victim, or risk getting shot. Often, they will shoot their victim with the victim's own gun because of this.
So really, all evidence points towards firearms, and weapons through relatedness, being ineffectual, and often detrimental, to self-defense. At best, it's just correlation, with an increase of weapons being correlated with increased crime. Although it's highly unlikely it's that simple. At worst, an increase of weapons increases the severity and quantity of crime. Which is noticeable with current evidence.
Since the ban has been instated the upward trend in fire arm homicide has been reversed and firearm related homicide in Australia is at an all time low.
http://www.aic.gov.au/statistics/homicide.html
If you noticed although the gun related homicides dropped, the rate of homicides actually stayed very consistent with the trend that began before the ban was even instated.
Gun related homicide is merely 10% of that of USA's.
http://en.wikipedia.org/wiki/List_of...ted_death_rate
Let's not forget to mention that crime rates have dropped in the US without the help of a gun ban. Almost 70% of homicides in the US are gun related, but that's only because of the availability. That doesn't mean the same amount of homicides can't be committed with other weapons or illegal firearms.
A long term policy cannot be determined by just 12 months of observation. Obviously there will be a knee jerk reaction.
Each country is a separate entity and you definitely can't say "a country with less guns has less gun incidents", but taking any individual country you can say "if there was less guns there would be less gun incidents" - barring if a country is an active warzone of course!
The point I brought up is that the amount of guns does not coordinate with the amount of homicides. The amount of homicides is based more on factors like police effectiveness, social standards, political situations, and things like that.
I've robbed you at gunpoint. You pull a gun out and shoot me in the back when I'm running away. Congratulations, you're now a murderer.
I fail to see how having a gun changed anything for the better.