During its development, this one was called the 6mm Winchester, but when introduced in 1955, its name had been changed to .243 Winchester. The .243 along with the 7mm-08 Remington and the .358 Winchester, are offspring of the .308 Winchester case. Of the many new cartridges introduced since World War II, the .243 and the 7mm Remington Magnum probably gained quicker and wider acceptance by hunters around the world than any other cartridge.
As popular opinion long had it, the .243 and the other 6mm cartridges of like performance shot flatter, bucked wind better, and delivered more energy to distant targets than cartridges of smaller caliber such as the .22-250 and .220 Swift. But the argument ends fast when the topic of conversation turns to flexibility. After varmint season is over, a rifle in .243 can switch roles and becomes a deer rifle, something that can not be said of a rifle of smaller caliber.
The .243 Winchester has a reputation for excellent accuracy, mainly because of the many excellent bullets available for it and because most shooters find it a pleasant cartridge to shoot. For loading varmint weight bullets up to 87 grains, H380, IMR-4064, and IMR-4320 do a fine job. For big game loads with 90 to 101 grain bullets, H4831, H450, H4350, H414, IMR-4350, and IMR-4831 are good choices.
The 243 Winchester was introduced by Winchester in 1955 for their Model 70 bolt action and model 88 lever action rifles. The 243 was quickly adopted by Savage for their Model 99 lever and Model 110 bolt action rifles. All of the British and European manufacturers began chambering bolt action rifles for this round. In fact, even Remington, who developed their own 6mm, had to recognize the popularity of the 243 and started chambering their rifles for it. The 243 (6mm) Winchester is nothing more than the 308 Winchester case necked down. Original development and publicity was due largely to the efforts of gun writer, the late Warren Page, who along with other wildcatters worked out a similar version before Winchester. The 243 is probably chambered in more different rifles than any other cartridge, except possibly the 30-06 Springfield. All other manufacturers of rifles offer this caliber.
The 243 Winchester represents a successful effort to develop light deer rifle caliber that could hold its own with the high velocity 22`s for long range use on small targets and still be adequate for larger animals. The 243 does this job well. It eliminates the need to own two rifles for anything from small game and pests up to and including deer size animals. The 257 Roberts and the 250-3000 Savage are supposed to cover the same range and certainly do. However, the 25 caliber bullets don`t have the same sectional density for long range varmint shooting until bullet weights get up to 120 grains., and then the velocity falls off badly All major domestic and overseas manufacturers of commercial ammunition offer this caliber. Its popularity as a deer caliber has prevailed over its varmint capabilities.