Yes of course a .222 can kill them but ...

I started off with my Remington 788 .222 and used it on a lot of feral goats.

But eventually worked out having to chase down the wounded ones and lost one or two ( or more, don't remember), and of course the best ever billy I shot ran off and I couldn't find him in the bush, decided my later .30-06 was much better. As they didn't run off after chest shots and if they did only a short distance.

I've brain shot deer with a .22 Mag. Oneday had a buck sit up when I went to cut his throat. Gunned up to the .222 as a minimum after that. The .222 usually shatters the skull a bit as well. A precision bigger calibre is also still better for brain shots. A .22 can kill a fallow well with a broadside shot to the heart with the proper point of aim. A bad shot means the deer runs off and can be lost.

Precision shooting works. When shooting a bunch of ferals, it isn't usually precision shooting. Loosing wounded beasts can happen no matter what, but is cruel and should be lessened.

I would still use my .222 on occasion, but prefer my 6.5mm or larger.

In no way am I knocking Mick's post, just general and personal comments. The .222 can work well if used well. As Mick shows with a great pig.