First of all, tougher sentences will not work for most domestic violence...especially those that end in suicide. Kimveer Gill, Marc Lépine, intent on committing suicide...tougher sentences would have no impact on them. That's why prevention is most important.
Regarding the nine million guns that are still not registered, I have no idea what the source of that is. I've been told it's Gary Mauser, a Simon Fraser University criminologist who's a long-time anti-gun control advocate. At the time, before the laws were passed, the Government of Canada estimated that the number of gunowners was two million or so and the number of guns in Canada was seven million or so. Right now we have close to two million gunowners registered and seven million guns, so I have no idea what you're talking about.
Finally, I'm wondering, if those nine million guns are not registered, are the owners licensed? If they're not licensed, then is there a problem with the licensing system or are these gunowners who don't respect the law? Or do they have licences and they are not registering their guns? To me, this is a little absurd. Where does this number come from?