Preface
Six-millimeter cartridges are very popular for various shooting activities. Their low recoil and high velocity mingled with great ballistic performance make them optimal for many purposes. Today I intend to take a walk through a selection of popular six-millimeter cartridges and why you might want one over the others. Whether you find yourself considering a six-millimeter for your next purchase, or trying to diversify your 6mm collection I hope we might be of help.
Old School
If you grew up in the 60’s and 70’s you were likely to run into a .243 Winchester on a typical deer hunt. A derivative of the always popular 308 Winchester; the .243 has always been a popular low recoiling hunting cartridge. Launched about the same time from a competitor, the 6mm Remington was a less popular but comparable option. Both of these cartridges have stood the test of time, pushing their typical 70-100 grain bullet quite fast. Making them great for varmint hunting and smaller big game animals.
The characteristics of these cartridges often led to them being relegated to either a “ladies caliber” or something for new shooters. There is surely nothing wrong with that, but they certainly shouldn’t be looked at as a lesser cartridge. I would happily take a .243 on a deer hunt or something comparable, the lightning speed and flat trajectory would come in very handy.
Way back then, you could have purchased a Model 70 chambered in .243. These days there are rifles from nearly every manufacturer chambered in the cartridge. Whether you want a bolt-action rifle from Savage or Sako, or even a lever-action .243 from manufacturers like Henry.
Modern Performers
If the .243 Winchester was such a good thing, and is still a popular chambering in todays modern firearms, you might ask why fix what isn’t broken? Hornady released the 6mm Creedmoor nearly ten years ago, much to the horror of the Creedmoor haters it took off. With a supply of high quality components it made sense. But what did the 6 Creedmoor have that the .243 didn’t already cover you might ask? Modern performance is the answer, Creedmoor’s came with aggressive twist rates like 1:8 and 1:7.5. The .243 has a slower twist rate which limits its ability to stabilize many modern bullets larger than 100 grains. The faster twist allowed the 6 Creedmoor to push bigger bullets like 108’s and 115’s at fantastic speeds, giving it a huge ballistic advantage.
One of my favorite 6mm cartridges is the 6mm GT. After the success of cartridges like the 6mm Creedmoor and competition cartridges like the 6 Dasher and 6 XC, the 6mm GT was released by GA precision and produced by Hornady. Finding a happy medium of performance and longevity, the 6GT fits easily into AICS magazines like the others I just mentioned. It does this while giving excellent ballistic performance and better barrel life than larger cartridges.
All of these modern performers are shorter cartridges than the older .243 Winchester, which allows them to load longer higher ballistic coefficient bullets and feed from magazines. And the smaller powder charges allow longer durability before the chamber throat is eroded causing degraded accuracy.
Modern Sporting Rifles
Any of the cartridges mentioned today could be and frequently are chambered for semi-automatic rifles like the popular AR pattern. I would be remiss if I didn’t mention the very popular 6mm ARC, as it is the most likely to fit into this category. For a variety of reasons, but mainly because it fits in a 5.56 sized action and magazine. The 6 ARC offers 6mm attributes like ballistic performance and heavier bullets while still fitting into the average AR15 rifle.
Additionally due to its smaller size, it burns far less powder extending the accuracy life of the barrel. This makes even more sense in a semi-auto as they tend to shoot much higher round counts than typical bolt-action rifles. There are a great variety of 6 ARC autoloading rifles available like the CMMG Resolute series of rifles.
The 6 ARC can obviously be used in bolt-action rifles as well, where it does an excellent job. Additionally the 6 ARC is also typically given a 1:7.5 twist which helps it handle modern bullet selections. I am a bit partial to the Howa Mini, a rifle we have used with great success. But there are also great bolt-action options from Ruger and Savage Arms. With the cartridge gaining in popularity every day, you are likely to find six of one, and half a dozen of another.