Editing Base bleed (section)

== Function ==

Most (50–60%) of the [[drag (physics)|drag]] on an artillery shell derives from the nose portion of the shell. Artillery shells travel through the air at supersonic speeds; as the shell pushes the air out of its way, it creates [[shock wave]]s that bleed off the shell's kinetic energy and therefore reduce its airspeed. [[Aerodynamics|Shaping the shell properly]] effectively reduces this component of drag; however, in regular flat-base artillery shells, the other large component is the so-called "base drag", caused by the low-pressure ("suction") area created directly behind the shell as it travels through the air.

Base drag can be reduced --without significantly extending the base of the shell or profiling it (as is done with [[Sabot (firearms)|sabot projectiles]]) by adding a small ring of metal extending just past the base, and placing a small [[gas generator]] to the rear part of the shell. The gas generator provides little to no [[thrust]], but fills the vacuum in the area behind the shell with an inflow of gas, dramatically reducing drag.

This means that, at a cost of only very little space to fit the gas generator in the casing,
* a longer effective firing range can be achieved with the same amount of propellant
* less propellant is needed to achieve the same effective range as with normal munitions
* heavier shells can be fired to the same effective range