In factory loadings, a 55 grain Nosler ballistic tip from a .243 is ballistically superior to any .204, .22-250, or .220 Swift loading. Thisincludes wind drift and bullet drop. Higher diameter bullets have higher ballistic coefficients, up to a point. With this in mind, if you really wanted a long range coyote gun a .338 Lapua would be hard to beat. However, a .243 or 25-06 is more capable than most people can shoot them. If I were you I'd take your .243 to a gunsmith for some bedding and a trigger job, find a load it likes, and practice. What kind of rifle is it, anyway? Also, where are you currently living? If you live in good elk/deer/pronghorn country and just want a new rifle, find a nice 7mm/300 Mag and shoot an aerodynamic bullet through that. It would serve you well for larger species, along with being a pretty good long range gun on the dogs.