Sometimes in wide-open country varmint shooters need a cartridge that will reach way out there with authority.
Riflemen, especially varminters, have always liked to try to hit targets that are a little too small and a little too far away. Today, the development of affordable laser rangefinders, riflescopes with special reticles and super-accurate rifles have greatly extended the reach of varmint shooters. And while mild-mannered cartridges such as the .22 Hornet and .223 Remington are great for general varminting, extreme long-range specialists go for bigger cartridges that shoot flatter, hit harder and shoot bullets that do a better job of resisting deflection on breezy days.
Cartridges of .22 and 6mm caliber--capable of burning enough powder to send heavy-for-caliber bullets with high ballistic coefficients--rule the roost, and a number of excellent choices are out there.
Among the .22s, the .220 Swift has long been my favorite, mainly because I have had such good luck getting rifles chambered for it to shoot inside half-minute-of-angle, but the .22-250 and .224 Weatherby Magnum are in the same league.
Moving up in bullet diameter, 6mm candidates start with the excellent .243 Winchester and 6mm Remington and end with the .240 Weatherby Magnum and a couple of wildcats: the 6mm-284 and 6mm-06.
Although less popular, the .25s, especially the .257 Roberts and .25-06, are worthy of consideration. The .22s generate less recoil, but the .24s and .25s are quite comfortable to shoot in a heavy rifle.
One of my favorites for reaching across a western canyon and surprising a rockchuck is built by Lex Webernick of Rifles Inc., around a Remington 40X action. Chambered in 6mm-.284, it weighs only a couple of ounces shy of 20 pounds. I can shoot it all day long without stress or strain.
The above exterior ballistics chart on the .220 Swift illustrates the advantages of using a heavy-for-caliber bullet with an extremely high ballistic coefficient for long-range shooting. Even though the Sierra 80-grain MatchKing exits the muzzle of a rifle in .220 Swift 600 fps slower than the 55-grain spitzer boattail, it shoots just as flat, delivers considerably more energy and most important of all, it does a much better job of bucking wind.
Extremely long bullets require barrels with faster-than-typical rifling twist rates. Top-notch options are available from a number of aftermarket barrel makers such as Lilja, Schneider, Hart, Shilen and Krieger.