Ballistics and Game Weight.

The Hornady Ballistics site can calculate some valuable information about your hunting bullet but it does not determine the game it can kill at the velocity/energies listed. I have researched tools to aid in finding the Optimal Game Weight for a given load and distance. I have last month published articles on Sectional Density and other methods to quantify the game size/weight.

In the book, Big Game Rifles and Cartridges, the author Edward Matunas presented his famous formula: Where Velocity cubed (V³) multiplied times bullet weight squared (W²) was further multiplied by 1.5 times 10 to the minus 12th. The formula was put forth again in the Second Edition of “Applied Ballistics” by Bryan Litz

Optimal Game Weight (OGW) = V³ x W² x 1.5 x 10¯¹²

For those of you who have a XL spreadsheet and want to play with this formula, you can do so. What is not covered in this formula is the effect of mushrooming of a bullet as it penetrates and on its killing effects. Or the effect of less than full penetration if the bullet separates on entry. The value of a large wound channel and the value of hydro-static shock, on vitals is absent, which are key elements not included but the fundamentals of velocity, bullet weight and momentum.

I played with add on’s to the formula but without specifics; they were “what if” games. What if the bullet mushrooms to 1.5 times the size of the bullet diameter which often occurs in hunting bullets? What if the bullet does not fully penetrate? What then?

In order for this formula above to work well, the bullet must be constructed so that it will not come apart in the animal and that it will mushroom creating a large wound channel. I like my bullets to penetrate with ample power and hydro-static shock so there is an obvious blood trail. Further that Sectional Density is considered in choosing a bullet where SD= Weight of Bullet in grains (converted to pounds) and divided by the Diameter Squared.

For deer the ideal SD is around 2.5 and elk above 2.5 and Moose 3.0 or higher.

After that the calculation should be; How far can I shoot the animal and ensure a clean kill remembering the need for mushroom and hydro-static shock. Some bullet designers have lead bullets that mushroom at 2000 fps and that hydro-static shock occurs s in the same speed range or faster.

Even Chuck Hawkes has a section on this;

Just remember, a small marginal bullet in the vitals is better that an more than adequate big bullet in the big toe especially if the animal wants to seek retribution on the hunter.




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About Ed Hale

I am an avid hunter with rifle and Bow and have been hunting for more than 50 years. I have taken big game such as whitetail deer, red deer, elk, Moose and African Plains game such as Kudu, Gemsbok, Springbok, Blesbok, and Impala and wrote an ebook entitled African Safari -Rifle and Bow and Arrow on how to prepare for a first safari. Ed is a serious cartridge reloader and ballistics student. He has earned two degrees in science and has written hundreds of outdoor article on hunting with both bow and rifle.