6.5mm Creedmoor

The 6.5mm Creedmoor was drawn up at Hornady in 2007 by Dave Emary with Dennis DeMille of Creedmoor Sports, for competitors who wanted a long, high-drag-efficiency 6.5 mm bullet out of an unmodified short bolt action. It is a .30 Thompson Center necked down, and almost every decision in it is about where the bullet sits rather than about how fast it goes.

The constraint is the magazine. A short action feeds a cartridge about 71 mm long, and the C.I.P. maximum overall length here is 71.76 mm — so the case had to be cut back to 48.77 mm to leave the bullet somewhere to be. The neck that remains is long enough that even a 140-grain match bullet can be seated to magazine length with its base still inside the neck rather than down in the body, which is the whole reason for the geometry: a bullet that sits below the neck-shoulder junction eats powder capacity and, on a case reloaded many times, sits against the thickened brass that forms there. The shoulder is steep, 30 degrees a side, and the head is the .308 Winchester head at 11.95 mm, so a rifle changes chambering with a barrel and nothing else.

That last property is what took it out of competition. In October 2017 US Special Operations Command tested it against 7.62x51mm NATO and .260 Remington in SR-25, M110A1 and Mk 20 rifles, and reported roughly double the hit probability at 1,000 m with about a third less wind drift; because the two rounds share magazines and bolt face, converting a semi-automatic sniper rifle meant a barrel swap. Adoption followed in 2019, and the round has since been given the US designation XM1200.

Gaps on this page: the two loads recorded here are the encyclopedia’s own ballistics table, which states a single 28-inch test barrel for every row and names Hornady, SAAMI and C.I.P. as its sources without saying which row came from which — so both velocities are attributed to the article rather than to a manufacturer datasheet. No ballistic coefficient is recorded, because none of the sources reachable for free publishes one tied to a specific factory load. The C.I.P. figures transcribed here are the European maxima; SAAMI’s ceiling of 62,000 psi is measured by a different method and is noted rather than stored as a second value.