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Ammo Brief: 6mm Creedmoor

Gun Digest Editors

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Spawn of the highly popular 6.5 Creedmoor, the smaller 6mm Creedmoor has the assets to go the distance.

What The 6mm CM Offers Precision Shooters:

The 6mm Creedmoor was the putative brainchild of gun writer John Snow, who began developing the wildcat publicly in 2009 as a magazine article project. But Snow, himself, explained that the idea began as far back as 2007, when the 6.5 Creedmoor had been introduced, and it’s likely that a lot of shooters simultaneously had the notion to neck down the 6.5 Creedmoor case to accept .243-diameter bullets.

Other mild case changes in the 6mm Creedmoor include pushing back the 30-degree shoulder 0.022 inch, which, likewise, shrinks the shoulder diameter 0.002 inch. Both have a maximum case length of 1.920 inches. In early 2017, Hornady introduced 6mm Creedmoor factory ammo; this makes sense, because the company had been instrumental in producing the original wildcat version.

Snow’s 6mm Creedmoor wildcat was originally chambered in a custom rifle built by George Gardner, owner of GA Precision. The major rifle components were a Sako 85 action, McMillan stock, Bartlein barrel, Surefire muzzle brake and sound suppressor, along with a Warne custom, one-piece 20 MOA Picatinny rail. However, it soon began winning Precision Rifle Series (PRS) competitions, because its extremely long, high-BC bullets could be chambered in AR-10 rifles, and PRS matches have a time component.

On-Target Ammunition Information:

The 6 CM succeeds at long distances at which the .243 fails. In the .243, when loaded with target bullets to full length, cartridges won’t fit in an AR-10 magazine—a problem the 6mm Creedmoor solves. It’s this success that has propelled the 6mm Creedmoor to its recent commercial acceptance. It’s reported that more than a million pieces of 6mm Creedmoor brass have already been sold.

General Comments

The 6mm Creedmoor is a near twin of the .260 Remington, but the former has about 5 percent less internal volume than the latter. The 6 CM performs much like the .243 Winchester and the 6mm Remington, pushing 100- to 108-grain bullets to around 3,000 fps from the muzzles of 24- to 26-inch barrels. But the 6 CM will shoot long, high-BC bullets accurately at long distances with the right twist rates of 1:7 and 1:8. Several makers are producing factory rifles in 6mm Creedmoor, including Browning’s X-Bolts, Seekins Precision Havak, Barrett Fieldcraft, Savage 10 BA Stealth Evolution, Bergara Premier Series Long Range, Ruger Precision Rifles and Ruger American Predator. Semi-auto rifles include the Savage Arms MSR 10 Long Range and Franklin Armory Militia Model Praefector-M.

Editor's Note: This article is an excerpt from Cartridges of the World, 16th Edition.

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