I'm also in the "get .22" camp. I would also add a 9 mm pistol. That caliber will be the most common available, other than .22, in a SHTF situation.
Other than Jan and Feb, I've had no problem getting 9 mm ammo. Yes, it's been expensive, but ther is a ton of it out there in closets and gun vaults.Please understand that I am not trying to pick on you here,
The shit has only mildly splattered the fan, and their is no 9mm or .22LR any where, for the last nine months.
Every one on this site needs to consider the lesson that has been such a current event for all to see.
When the SHTF Their will be very little "readily available" ammunition other than what you yourself are in possession of.