Actually, if you're considering an M6 AND a second revolver, you'd do better to make the revolver a .357. This would give you a better self defense tool, that would still do double duty as a hunting gun. But the M6 would be a MUCH better choice than any .22 pistol as long as your pack was big enough to carry it concealed.
Another option to the M6 is the Rossi Matched Pair, which is a .22 rifle with a second shotgun barrel in .410, 20, or 12 gauge. I've had both the M6 and the Rossi (.22/.410), and the Rossi definitely has the better trigger. Also, the Rossi is only about $140.00, while the M6 is around $180.00. There are advantages to both guns. With the M6, the weight is slightly less, and you have both barrels immadiately available. With the Rossi, you need to switch barrels if you want to shoot shotgun instead of rifle, but you have the benefit of larger gauges.
The only real downside of the Rossi is the plastic sights. I replaced the rear sight on mine with a steel buckhorn rear from another .22 rifle, and epoxied the front sight blade in place, once it was adjusted properly for height. One other advantage of the Rossi is that you can get a spare barrel in .357, and *possibly* other calibers as well. I'm still checking on that.
For a pure survival gun, the M6 would be the better choice, especialy backed up with a centerfire revolver. For a weekend plinker AND pot gun, the Rossi would get the nod. And once the sight situation is taken care of, the Rossi shoots extremely well.