6mm Optimum

The "6mm Optimum" is a concept popularized in 1999 by military writer Stanley C. Crist.

The 6mm AR (center) is near the "6mm Optimum".

History

Crist argued for the adoption of a 6mm rifle chambering as a replacement for the venerable 5.56×45mm NATO and 7.62×51mm NATO, calculating that such a loading would be near the weight and minimal recoil of the lightweight 5.56 while nearer the terminal performance of the heavier 7.62, thereby permitting a single caliber to serve in general-purpose machine guns, sniper rifles, and infantry carbines.[1][2]

Ballistics

Crist's specifications were that "6mm Optimum" ammunition achieve, with a 100 gr (6.5 g) bullet:

• Muzzle velocity: 880 m/s (2,900 ft/s)
• Velocity at 1200 m: 350 m/s (1,149 ft/s) (slightly over the speed of sound)
• Muzzle energy: 2,531 J (1,867 ft⋅lbf)
• Energy at 1200 m: 397 J (293 ft⋅lbf)
• Flight-time to 1200 m: 2.21 seconds
• Deflection at 1200 m: 3.8 m (151 in) in 4.5 m/s (10 mph) wind speed
• Maximum trajectory height: 6.2 m (244 in)

...of which he noted, "...even with a conservative estimate for the muzzle velocity of the 6mm Optimum cartridge, computed data for 1200-meter velocity, flight-time, wind-deflection, and trajectory height are all greatly superior to both 5.56 and 7.62 NATO rounds."[1]

See also

• Ballistic table
• 6mm PPC
• 6mm AR
• 6mm ARC
• .243 Winchester Super Short Magnum
• 6 mm XC
• 6×45mm SAW
• 6-6.5x47 Lapua
• 6mm Lee Navy
• 6 mm caliber
• List of rifle cartridges
• Table of handgun and rifle cartridges

References

1. Crist, Stanley C. (September 1999). "Is 6mm the Optimum Caliber? A common Cartridge for Rifle and Machinegun" (PDF). Infantry. 72 (3). Archived (PDF) from the original on January 25, 2017. Retrieved September 15, 2020.
2. "6mm Optimum Cartridge". C. Meyer. October 11, 2002. Archived from the original on January 24, 2020. Retrieved September 15, 2020.