6mm Creedmoor

Lightweight Bullets in the Newest “.243”

- Jim Matthews

The 6mm Creedmoor was designed for long-range target shooting with long and skinny, heavy-for-caliber bullets that slip through the air with the greatest of ease. Wind affects these bullets little; they just fly right through it, almost unaffected.

Grumpy old shooters will argue that if the ancient .243 Winchester was loaded to the same pressures as the Creedmoor, and you screwed on a barrel with the same fast twist rates as the Creedmoor, the .243 Winchester would effectively be the same cartridge, but with the sagging shoulders that seem to come with age.

Ballistically, there is not much difference between the two cartridges. An inch or two of barrel length will have more of an impact on velocity than the difference in case capacity. Several pieces of Hornady 6mm Creedmoor brass held an average of 53.25 grains of water while the same number of Federal .243 cases held an average of 54.25 grains of water. The nearly 2 percent difference isn’t enough to sneeze about. A handloader will see that difference between brands and lots of brass for any cartridge.

So what is the point of the 6mm Creedmoor if it’s really just a shorter, sharper-shouldered .243? There is one primary answer to that question: barrel twist. The Ruger American Predator 6mm Creedmoor, one of the first major factory rifles available for the new 6mm round, was used for hunting and load development for this story. It has a 1:7.7 twist rate. Pouring over catalogs, it was impossible to find anyone chambering the 6mm Creedmoor with anything slower than a 1:8 twist, and some manufacturers were even using 1:7 twist rates or faster to stabilize bullets like the Berger 115-grain VLD Match or Sierra 110-grain MatchKing.