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Tuzo · February 12, 2012, 11:23 PM

This is how an aeronautical engineer explained the efficiency of a hollow point boat tail rifle bullet fired at supersonic velocity. The hollow point creates a boundary layer of compressed air resulting in air on air interference. In other words, the point of the bullet is "self-adjusting" and air flow becomes laminar. A sharp pointed bullet, such as polymer tipped, will respond to variations in point shape such as slightly bent tips and scratches because air flow becomes turbulent.

However, a surface with turbulent air flow acts as a boundary layer to laminar air flow above the turbulent. An example is a boat hull that has been wet sanded below waterline. It will perform more efficiently than a shiny smooth hull because the turbulent water layer created by a roughter hull surface acts as a boundary for water flowing over that layer. This results in water-to-water contact and decreased friction.

February 12, 2012, 11:23 PM	#10
Tuzo Senior Member Join Date: June 14, 2007 Location: Louisiana Posts: 797	Hollow point accuracy This is how an aeronautical engineer explained the efficiency of a hollow point boat tail rifle bullet fired at supersonic velocity. The hollow point creates a boundary layer of compressed air resulting in air on air interference. In other words, the point of the bullet is "self-adjusting" and air flow becomes laminar. A sharp pointed bullet, such as polymer tipped, will respond to variations in point shape such as slightly bent tips and scratches because air flow becomes turbulent. However, a surface with turbulent air flow acts as a boundary layer to laminar air flow above the turbulent. An example is a boat hull that has been wet sanded below waterline. It will perform more efficiently than a shiny smooth hull because the turbulent water layer created by a roughter hull surface acts as a boundary for water flowing over that layer. This results in water-to-water contact and decreased friction.