With the addition of clinometers fixed machine gun squads could set long ranges and deliver plunging fire or indirect fire at more than 2,500 m (2,730 yd). This indirect firing method exploits the maximal practical range, that is defined by the maximum range of a small-arms projectile while still maintaining the minimum kinetic energy required to put unprotected personnel out of action, which is generally believed to be 15 kilogram-meters (147 J / 108 ft⋅lbf). Advanced planned and unplanned map and range table predicted support/harassment firing methods developed during World War I like plunging fire or indirect fire were not as commonly used by machine gunners during World War II and later as they were during World War I.