A method and apparatus for installing a fixture, such as a flash suppressor, to the threaded muzzle end of a firearm barrel. A chart or "timing wheel" is directly placed to the fixture when hand tightened to the firearm's muzzle end without any shims placed thereon, the chart identifying the appropriate shims to be placed on the barrel's threaded muzzle end portion for positioning the center of the flash suppressor vent substantially at top dead center with respect to the barrel when a predetermined torque is applied to the flash suppressor.