I disagree. We are talking rifles. 25 rounds of just about anything will work for SD.
You have to hit a very small area to be effective with a .22. 25 chances will not be enough. Observe
The guy emptied two pistols at POINT BLANK range and the lawyer walked away. One round from a .45 makes a big difference in what the bad guy does afterwards. A whole bunch of .22 rounds may not make any difference at all. Sure it "might" work. But "might work" is nowhere near good enough. "Almost certainly will work" is my idea of a proper SD weapon.
Let's talk shotguns for a second here. You can fire 9 pellets (or more actually) each the size of a .32 bullet or so all at one time. If you miss you can fire again just like with your .22. Some of those shotguns hold 25 shells each with nine "00 buck" pellets inside. Just one hit from a shotgun is almost certain to disable a bad guy. Why on earth would you choose something that has a very small probability of doing that instead of the one that almost certainly will work? It makes absolutely no sense. Even if a 12 ga. is too much for you there are smaller ga. shotguns. Almost every adult can fie a 20 ga. shotgun effectively.
It just makes ZERO sense to use a .22 when you can use a shotgun instead. You can also hunt more effectively with a shotgun. Sure if you're good enough you can hunt enough game with a .22 to keep you going for a short time. But I'm here to tell you that game gets thinned out extremely fast especially if you think you can just take off from a city and take up residence in the woods somewhere. The people that own those woods are likely to take extreme exception to that in times of SHTF stress. I know I would. You wouldn't hunt on my property for long. The small amount of game a given stretch of woods supports is barely enough to keep one or two people going for a month. You better know how to do something besides hunt because you won't find enough game to keep you alive. Trust me I grew up on a farm where we supplemented our diet with game. We limited ourselves to the hunting season and it was still slim pickings for things like squirrels. They don't reproduce like rabbits and rabbits get hunted out extremely fast as well. I've seen it happen friend. You'll want to learn to build a fish trap, gig frogs, set a trot line, set up jugs, and learn just how drunk you have to be before noodling seems like a good idea.
I grew up getting a fair portion of our food from the land. Unless you're hunting deer that food will dry up quick. And it's not that easy to kill a deer with a .22.
Listen to the voice of experience. You'll need a bigger gun at least part of the time. And I'd carry a handgun for SD all the time and it would NOT be a .22. Double that to a .44 and you're getting close. Make it a magnum and you're there.