ⓘ 6mm Optimum. 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 ..

                                     

ⓘ 6mm Optimum

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. Ballistics

Crists specifications were that "6mm Optimum" ammunition achieve, with a 100 grain bullet:

  • flight-time to 1.200m: 2.21 seconds
  • maximum trajectory: 244 inches
  • deflection 1.200m in 10 mph crosswind: 151 inches
  • velocity: 2.900fps muzzle, 1149fps 1.200m
  • energy: 1.867 ft-lbs muzzle, 293 ft-lbs 1.200m

.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."