It depends on what you call Humanely. If you can place the shot in the ear then no sweat. Heart lung might be reasonably quick but certainly not instantaneous. .22 Mag would be a bit more positive.

Do you realy need to worry about noise level? If so the .22Lr caries quite a distansce also.

1 .223 as opposed to several .22's is quieter. IMHO

Good luck

I use a 5.56, I have seen them dropped with a .17 WMR, but not a .22LR. 1 sure hit versus 1 possible or just wounding is perfered.

Well, I have my Rem 7400 30-06 deer rifle, M1A, M1 Garand Tanker (.308), AR15, or even the M-1 carbine to choose from, besides all my 22LRs.

Thanks for the responses. I think I've only seen one coyote in my yard so I am not sure how big they get. I certainly don't want to only wound anything.

This could be a good excuse to get a Rem 700 varmiter in .223. I only have 22LR bolt actions. The wife gave me the go ahead to get whatever I needed (she was fond of the cats), but I figured I must have something I could use already.

That and the fact that I just picked up 2 Springfield XD sub compacts...

Personally, I hate coyotes. I don't care how they die, as long as they die. If you can get close enough, shootem with a .22. They'll die. If they're too far away, get something with more range. The 17HMR or 22 mag would be the next step up, and they're both fun to shoot.

If noise is an issue I'd get a 22 Hornet otherwise a 223.

Just don't use the .22 LR. Chances are you'll just wound it and that's just not humane or acceptable.

Almost anything else will do. Have a revolver? It's be a cool excuse to get a 4 or 6 inch .357 and get good with it