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

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

History

Crist argued for the adoption of a 6mm service 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 (.223 caliber) while nearer the terminal performance of the heavier 7.62, thereby permitting a single cartridge 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

References

  1. 1 2 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.
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