The .243 Winchester is a very popular sporting rifle round. It is ideal on game such as Whitetail deer, Mule deer, Pronghorn antelope, Black bear and wild boar. In the USA it is very effective for long range varmint shooting. It uses what is basically a .308 cartridge case necked-down to accept a .244 in/6 mm bullet. The .243 is well known for its accuracy, very flat trajectory, and relatively mild recoil compared to other cartridges. In Southern Africa the .243 was voted as the most popular hunting cartridge in South Africa, Namibia and south-western Botswana, because of its long range capabilities and effect on game in the Springbok/Blesbuck category where ranges can reach in excess of 300m.
This cartridge was first introduced in 1955 for Winchester's Model 70 bolt-action sporting rifle, and it quickly gained popularity among sportsmen worldwide. Even Winchester's chief competitor, Remington, was quick to chamber rifles for the .243 round, and all mass-market riflemakers have followed suit. Many companies offer a selection of rifle models chambered in .243 Win.
Since the enactment of the 1963 Deer Act in Great Britain, which stipulated a minimum bullet diameter of .240 in together with minimum levels of muzzle velocity and bullet energy, the .243 Win. has been perceived by UK sportsmen as the "entry level" calibre for legal deer-stalking; and since the 1960s the .243 has been by far the most widely used calibre for shooting small and woodland deer in the UK.
Firearms that would normally be chambered for the .308 Winchester/7.62x51mm NATO caliber are distributed chambered for the .243 cartridge in Countries whose regulations restrict or forbid civilian ownership of "military calibers"; examples of countries with such legislations are France and Spain.
In a non-sporting, non-civilian context, bolt-action rifles chambered for the .243 Win. were utilized by the Los Angeles Police Department's Special Weapons And Tactics (SWAT) unit during its early years.
.243 Winchester Improved and .243 Winchester P. O. Ackley created an Improved version of this cartridge called the .243 Winchester Improved (Ackley). Like other Improved cartridges, this created a steeper shoulder and blew the sides out, plus slightly lengthens the case, giving about 10% more powder capacity, and some small improvement in velocity. Both versions of the .243 cartridge are good for hunting deer.
The .243 Winchester produces a velocity of 2960 feet (902.21 m) per second with a 100 grain (6.8 gram) projectile from a 24-inch (610 mm) barrel. Commercially loaded .243 ammunition is available with bullet weight ranging from 55 grains (3.6 g) up to 105 grains (6.8 g), typical use being with bullets of c. 75–90 grains (6 g).
The .243 has gained very substantial popularity in the international hunting world, and commercially loaded ammunition is easy to find in almost any gunshop. Along with the .270 Winchester, the .308 Winchester, .223 Remington, and .30-'06, it is amongst the most popular and widely available of all centrefire cartridges. The .243 is a popular and successful choice for all but the very largest deer, small to medium sized antelope, and for varmint hunting.
In the United States, the cartridge is used extensively in varmint hunting as well as larger deer-sized game. It is also used with good effect in competitions out to 1,000 yards (914 m).