shot, or a deer a month, with .22 rifle and scope?
ever TRY braining a man,deer, or cow with a sling shot? Sure can with canned, scoped .22 unit in CAR-15, to 50m. Can cause a man to DIE with the .22 unit, by hitting him at 150m, too, and such a hit AINT hard to get, either. So he is able to run around for a few minutes, able to walk for an hour, etc, before the blood loss, fever, etc, bring him down, so what? He wont have a CLUE where to run or fire AT. 
Realisitcally, you can easily carry ALL the .22 ammo you have any HOPE of using for foraging,post shtf, and half of the ammo you find on the dead will be .22lr, for reasons of price, availability, effectiveness, bulk, wt, and ease of making a silencer-for.
when you find a guy with 12 ga, or 308, he'll have at MOST 50 rdsof 12 ga, much of it small birdshot, or 150 rds of 308, and neither one has much utility, post shtf. When you catch a guy with a .22, however, he's REAL likely to have MANY hundreds of rds of ammo on him.
Realisitcally, you can easily carry ALL the .22 ammo you have any HOPE of using for foraging,post shtf, and half of the ammo you find on the dead will be .22lr, for reasons of price, availability, effectiveness, bulk, wt, and ease of making a silencer-for.
when you find a guy with 12 ga, or 308, he'll have at MOST 50 rdsof 12 ga, much of it small birdshot, or 150 rds of 308, and neither one has much utility, post shtf. When you catch a guy with a .22, however, he's REAL likely to have MANY hundreds of rds of ammo on him.