Stopping Power Calculator For Hunters

The Effective Firearms Stopping Power Calculator For Hunters provides up to six (6) indices of bullet performance.

For a visual example, please view the YouTube tutorial:

Enter a muzzle velocity (feet per second) and bullet weight (grains) and it can display the bullet momentum, the muzzle (kinetic) energy, and the Matunas Optimum Game Weight (OGW). If you are checking a frangible varmint bullet, then the (V) checkbox can be set as the OGW uses a different constant factor for varmint loads."

Enter the caliber and you can also display the Taylor Knock Out Factor (TKOF), the Thorniley Stopping Power (SP), and the Hawks Killing Power Score (KPS).

If you also enter powder weight and the weight of the gun, an estimate for the free recoil energy is also available.

While all seven values (including the recoil factor) are available via the Internet, obtaining them would require visiting multiple web sites, which can be awkward while standing in a store evaluating ammunition options on the shelf, or impossible in an area where Internet service is not available.

Please send any questions, complaints, or corrections to
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What's New

Updated calibers
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Additional Information

Eligible for Family Library
Eligible if bought after 7/2/2016. Learn More
November 9, 2021
Current Version
Requires Android
5.0 and up
Content Rating
Mature 17+
Offered By
Effective Firearms
1507 E. 53rd St. Unit 911 Chicago, IL 60615
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