<prompt> The bore of a gun can be examined by:-Broach cutterHelixometerComparison microscopeSimple microscope  <response>: Helixometer: An instrument for inspecting the interior of a gun barrel and for measuring the rate of twist of the rifled bore of a firearm. Comparison microscope is used to match the marks in test bullet crime bullet Broach cutter is used to produce riflings in a gun. 