Sir Alfred George Greenhill (1847-1929)
You really depend on Greenhill's equation? You might want to read his 1908 treatise "Notes on Dynamics," which was used to describe the elliptical flight of lead-steel artillery projectiles, not lead-alloy bullets. Greenhill's work was mainly on elliptical functions, and was interested in their applications to dynamics, hydrodynamics, elasticity, and electrostatics.
Greenhill's "equation" negates friction caused by a projectile passing through the air; negates the earth's gravitational pull on the projectile; negates frictional forces of air acting counter to the rotation of the projectile; negates the inverse square law relative to gravity; assumes a terminal velocity of 2000 feet per second of a 6-inch ellipsoidal (egg-shaped) metallic shot that is 3.5 calibres in length, and a weight of 0.2 pounds (but of unknown mass density), then assumes the air density is 800 times the specific gravity of the metal. So if you want to base your new bullet design on "Greenhill's equation," good luck. There are other "equations" that have been attributed to Greenhill, but his equation relative to his Notes on Dynamics, was never intended as applicable to lead-alloy bullets. Greenhill taught in the Artillery College of the Royal Military Academy at Woolwich from 1876 to 1908.
First Cousin (7 times removed) to Brigadier General Stand Watie (1806-1871), CSA
1st Cherokee Mounted Rifles | Principal Chief of the Cherokee Nation 1862-66
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