Something like 60% of gun deaths in the US are suicides. You often hear the line that if access were restricted to guns, killing oneself becomes more difficult and thus less likely. There is some evidence for this being true. For example, the suicide rate among Israeli soldiers is reported to have decreased by a significant amount after they were disallowed from bringing their weapons home on the weekends. However, in broad terms, the US and UK (which I think are good comparables) have very similar suicide rates (about 12 per 100,000) despite their varying rates of gun access.

If I were advocating for gun control, I would focus on making it easier to hold gun manufacturers civilly liable for accidental deaths. Wikipedia says that there are around 500 accidental gun deaths per year in the US, which makes it far higher than, say, GM's recent ignition switch debacle (sure it's a fair point to say that accidental gun deaths mean that the gun worked as intended but in the wrong circumstance, although surely that's not always the case, as in misfires that are hanging, for example, where even experienced people could make a mistake). If I make a product, I'm responsible for what it does to people. It's frustrating to see gun manufacturers exempted from this law (as a citizen, I mean, independent of my stance on guns, I don't like it when free passes are given to one industry over another for political expediency).