Gundrills were originally applied in gun barrel machining but are now widely used in shipbuilding, automotive, engine, locomotive, military, chemical machinery, oil industry, mining machinery, and hydraulic parts industries due to their superior hole machining performance. The gun drill's unique tool construction eliminates the need to retreat the chip during deep hole machining, allowing the hole to be machined to depth all at once.
link:https://www.mariejcarbide.com/carbide-rod/tungsten-carbide-gun-drill/cnc-lathe-precision-deep-hole-drilling-bit.html