How to use SetHitPower(float) function listed in lua_help_ex?

[Orelarsen]

When I use it in my script it crashes with message : LUA error: ...anomaly 1.5.2\gamedata\scripts\charge_gauss_rifle.script:34: attempt to call method 'SetHitPower' (a nil value)

[Orelarsen]

Edit: this problem happens with all of these functions

[themrdemonized]

try obj:cast_Weapon():SetHitPower(4.2)

[Orelarsen]

Thanks a million, mister demonized.