[driftdiver]

Something in the .223 (or 5.56), .243, or .270 range would probably be the cheapest that would get you quick kills. These do represent a danger to neighbors though as the rounds can kill out to about 600 yds and will travel 1 1/2 miles.

A .22 would kill them but not quickly unless you can get within 75 yds and are good enough for a headshot.

[Still Thinking]

Something in the .223 (or 5.56), .243, or .270 range would probably be the cheapest that would get you quick kills. These do represent a danger to neighbors though as the rounds can kill out to about 600 yds and will travel 1 1/2 miles.

A .22 would kill them but not quickly unless you can get within 75 yds and are good enough for a headshot.

How about a 22 Hornet? About 4 times the energy of a 22 LR, but half or so of the normal full-size small centerfires. Even a 22 WinMag would be a step up from a 22 LR. I'd think that'd give you more range on the coyotes but still be safer for the neighbors.

[Last Dakotan]

.270 or anything based on the 30-.06 cartridge is overkill.

The .270 is designed to fly very fast and with very a flat trajectory - something it does very well. Large game - long distances.

The better option is a reliable platform in the .223 - .243 range.