The calculation assumes a "flat-fire scenario" (a situation where the shooting and target positions are at equal elevation), utilizing British military custom high-pressure .338 Lapua Magnum cartridges, loaded with 16.2 g (250 gr) Lapua LockBase B408 bullets, fired at 936 m/s (3,071 ft/s) muzzle velocity under the following on-site (average) atmospheric conditions: barometric pressure: at sea-level equivalent or on-site, humidity: 25.9%, and temperature: in the region for November 2009, resulting in an air density ρ = 1.0854 kg/m3 at the elevation of Musa Qala. Harrison mentions in reports that the environmental conditions were perfect for long range shooting, "... no wind, mild weather, clear visibility." In a BBC interview, Harrison reported it took about nine shots for him and his spotter to initially range the target successfully.