The .243 Winchester is one of the most successful rifle cartridges introduced in the last half of the 20th century. Winchester introduced it in 1955, on the then relatively new .308 Win. case, and it immediately became a best seller.

The smart money at the time was betting that Winchester would introduce a .25 caliber combination varmint/deer cartridge on the .308 case. But wildcatters, led by gun writer Warren Page, were experimenting with .24 caliber varmint cartridges (Page's was called the .240 Page Pooper, as I recall), and getting a lot of ink in the gun magazines. Winchester sensed the winds of change blowing, and necked down their .308 case to .24 instead of .25 caliber. The result was the .243 Winchester, and the rest is history.

The .243 case, like its parent the .308, is a rimless bottleneck design. Its rim diameter is a standard .473 inch, and it retains the 20-degree shoulder angle of its parent case. The case length is 2.0450 inches and the maximum overall cartridge length is 2.71 inches. SAAMI specifications call for a maximum average pressure of 52,000 cup.

The .243 Win. will cycle through almost any short action rifle, whether bolt, lever, pump, or semi-auto. The .243 has become a favorite of hunters who want to shoot varmints, predators, and deer size game with the same rifle. It has also become almost the standard long range deer and antelope cartridge for beginning hunters. Recoil energy is low, about 10 ft. lbs. for most loads, and trajectory is flat, both of which contribute to the .243's reputation for deadly practical accuracy.

Some years ago I did a survey of all the new centerfire hunting rifles sold at that time, and the .243 Win. was chambered in more models of new rifles than any other cartridge. It is the sixth best selling CF rifle cartridge in the U.S. on most sales charts. One of that very elite group of calibers often chosen by folks who, for one reason or another, can only have one centerfire rifle. Along with the .270 Win., .30-30 Win., .308 Win., and 30-06 Spfd., .243 Winchester ammunition can be bought just about anywhere in North America, or the world, that ammunition is sold. .243 ammo is produced in North America, Europe, Africa, Australia, and probably other places.

In .243 caliber the 55 to 80 grain bullets are the varmint bullets; the 90 to 115 grain bullets are designed for medium size big game, and the 85-87 grain bullets can be either (but not both). The Speer 80 grain spitzer has a ballistic coefficient (BC) of .365 and a sectional density (SD) of .194; the Speer 100 grain big game spitzer bullet has a BC of .351, and a SD of .242. These are pretty good numbers, superior to the numbers for the same bullet weights in .25 caliber.

The .243 is a better varmint cartridge than the .25's, while remaining adequate for deer and antelope. The .243 launches an 80 grain varmint bullet at a muzzle velocity (MV) of about 3,350 fps. This means that it shoots about as flat as a .22-250, only its 80 grain spitzer bullet has a BC of .365, compared to the 55 grain .22 spitzer's BC of .255. This is an enormous difference, and explains why the .24's are so much better than the .22's on windy days.

When using the .243 to hunt medium size big game animals, bullet selection is paramount. The varmint bullets will not give adequate penetration and must be avoided. On the other hand, rapid (but controlled) expansion is very important, as the small diameter 6mm bullet has little shocking power if it does not expand and expend its energy inside of the animal. Two bullets in the 90-100 grain weight range that have earned a good reputation on medium size big game animals are the Remington Core-Lokt and Nosler Partition.

Winchester's Supreme 95 grain Ballistic Silvertip big game bullet is factory loaded to a MV of 3,100 fps with 2,021 ft. lbs. of muzzle energy (ME). If that load is zeroed to strike 2.5 inches high at 100 yards the bullet will then strike 3 inches high at 150 yards, 2.3 inches high at 200 yards, and 3 inches low at 300 yards. At 200 yards that bullet hits with 1,455 ft. lbs. of energy, and at 300 yards it still retains 1,225 ft. lbs. of energy. With this load so zeroed the .243 Winchester is about a 300 yard deer and antelope cartridge.

Reloaders with a .243 are in luck. There are bullets from 55-115 grains from which to choose, and many common powders are adaptable to the .243. Also, .243 brass is strong and plentiful.

According to the Nosler Reloading Guide No.5 their 80 grain Ballistic Tip varmint bullet can be driven to a MV of 3041 fps with 38.5 grains of H380 powder and 3291 fps in front of 42.5 grains of H380. The 95-100 grain big game bullets can be driven to a MV of 2909 fps with 37.5 grains of IMR 4350 powder, or 3060 fps in front of 41.5 grains of the same powder. The technicians at Nosler used Winchester cases and Remington 9 1/2 primers for their load development. The loads were chronographed from a 24 inch barrel.

There have been many modern cartridges, and especially short action cartridges, that were more hype than substance. The .243 is not one of those. It is a legitimately useful cartridge that deserves its enormous popularity.