You should be able to slow it down over-time. Make it illegal to sell guns, but for the people who've got guns now they're allowed to keep them. Make it illegal to carry a gun in public places (road, cafe, school, etc) and setup regulations for storage. Once people die who own weapons, they have to be handed to the government who can dispose of them properly. Besides that, increase responsibility for your guns (i.e. if your kid runs off with your gun and shoots half a school, expect jailtime at the very least).
If these are things I can come up with in about half a minute, I'm pretty sure a well-educated and large government can do much better!