Research from around the world is pretty clear: the more easily guns can be bought legally, the more people are killed with them. In the USA of course, some 20,000+ people are killed every year with guns; compared with something like 5 in Japan where guns are impossible to buy. Australia lies somewhere in the middle (in terms of per capita deaths). There was an article in the Australian a week or so ago where it was pointed out that in the six years before the buy back, there were 4 mass murders in Australia where guns were used, and (until yesterday I suppose), there were none in the six years after. I'm not sure what sort of statistical test you'd apply to that, but it is highly suggestive.
Also, there is little evidence that tougher penalties are a disincentive for crime, whereas the probability of being caught is.
I suspect, also, that there is a large impulse element in the risk of killing someone with a gun. The risk to ordinary people is not from some vast criminal underclass who can easily get guns from black market suppliers (also a doubtful proposition, since criminals, too, are ordinary people), but from an angry young man, probably in the victim's family or immediate circle, who has anger problems, who snaps, and with firearms in easy reach in the home, goes ahead and uses them - either on someone close, or himself (a vast number of the US gun deaths, for instance, are suicide).
Gun owners might not like it, but the solution is simple: control guns so tightly they cannot be bought except with incredible difficulty; license ammunition and mark all casings; and for good measure, offer counselling and psychological support to youths who demonstrate a bent for firearms just in the same way you would to boys who enjoy torturing small animals.
