I've always heard that .22LR is the ultimate survival cartridge, but I've had a lot of trouble over the years implementing it as such in my practice and study of survival skills. 9mm is much better and 22LR is too redundant with 9mm to even serve as an alternate or secondary weapon system so there's no point in using it at all.

22LR might be very light and compact and cheap, but it can't substitute 9mm because you still need an effective and reliable defensive weapon. That means it's mass and cost are EXTRA, so you're not actually saving any storage space or money with it. Even if we're just talking a 22 pistol, the weapon itself weighs 2 pounds empty by itself, I would rather just carry 3 more Glock magazines instead. On top of that, the 22 ammo that is consistently accurate from lot to lot, reliable, and shipped in packaging suitable for long term storage and transport under harsh conditions and which would actually be worth stockpiling and carrying for survival such as CCI minimag isn't even that much cheaper than 9mm anyway.

It's not a good a handgun cartridge. Handguns have always been my primary survival weapons because they are light and concealable and I can take them anywhere, and because I live in the Eastern forest region of the USA where visibility is extremely low. 22LR loses most of it's advantages in a handgun. It becomes extremely loud in short barrels, loud enough to need earplugs and to alarm people in the area. It loses it's accuracy, which is critical because it's a very small, low-energy bullet so it's only useful for headshots on anything larger than a squirrel. It would be very difficult to get close enough to a medium to large game animal to shoot it in the head with a 22 pistol, I would rather just use my 9mm for a heart/lung shot. It definitely works, no matter what you might believe.