Some years back the people at winchester were thinking the same thing"...You know there are hunters out there who want a rifle in a cartridgethat they can use for deer and also do some varmint shooting with the same rifle. A kind of deer/coyote gun you might say..."

And so they came up with the .243 win. cartridge. And now almost all serious manufactures chamber rifles in it.

So the .243 is a cartridge that is well suited for the task but you asked about the best "rifle" and there are so many good "rifles" out there.

Robin down under; where they build a wildcat, necking a .303 british down to .25 cal.. which would be a good deer/coyote round.