1) Firearm construction 
Gun drills are straight fluted drills which allow cutting fluid (either compressed air or a suitable liquid) to be injected through the drill`s hollow body to the cutting face. They are used for deep drilling—a depth-to-diameter ratio of 300:1 or more is possible. Gun barrels are the obvious example; hence the name. Other uses include moldmakin....
A drill, usually with one or more flutes and with coolant passages through the drill body, used for deep hole drilling.
A drill, usually with one or more flutes and with coolant passages through the drill body, used for deep hole drilling.