Hathcock generally used the standard sniper rifle: The Winchester Model 70 .30-06 caliber rifle with the standard Unertl scope. On some occasions, however, he used a different weapon: the .50-caliber M2 Browning Machine Gun, on which he mounted the Unertl scope, using a bracket of his own design.[8] This weapon was accurate to 2500 yards when fired one round at a time.
In 1967 Hathcock set the record for the 20th century's longest combat kill with a Browning M2 .50 BMG machine gun mounting a telescopic sight. The distance was 2,286 meters (2,500 yd / 1.420 mi). Hathcock was one of several individuals to utilize the Browning M2 machine gun in the sniping role. This success led to the adoption of the .50 BMG cartridge as a viable anti-personnel and anti-equipment sniper round. Sniper rifles have since been designed around and chambered in this caliber.