Maybe I'm in the minority here, but I'll toss this out. If you are moving back permanently and your choice is to leave the gun behind or try your luck with CBSA.. Why not try it? You're out a gun either way..
Now for the disclaimer
If they do sieze the gun, you can expect to be red flagged for just about every piece of mail you recieve from out of country.
Don't try to hide the fact that it's there.. Just put it in with your stuff, locked, unloaded would be best, with a battery in the case with it. Just looks a little more respectful. And if you try to hide the fact that you have the gun in your possessions, you are basically smuggling.
That's all. Probably not the best advice though.