International Standard Atmosphere
For a typical .408 CheyTac chambered gun, shooting 27.15 gram (419 gr) Lost River Ballistic Technologies bullets (claimed G1 BC = 0.940) at 884 m/s (2900 ft/s) muzzle velocity, the supersonic range would be 1930 m (2110 yd) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m3).