iPhone Muzzle Energy Computer

iPhone Muzzle Energy Computer

The top three rows above are active. Change any number and everything dependent on it will be recomputed. Click a button below to fill in values for the linked load. More ballistics for Remington ammo here.

Rifle:
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Handgun:
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Shotgun:
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Note: this page is entirely self-contained. It requires no server-side code to operate. All the computations are done by JavaScript code embedded in the HTML. If you "Save As..." in your browser, you can run it off-line.

Efficacy is a measure proposed by L. Neil Smith. It is defined as energy in foot pounds multiplied by projectile cross-sectional area in square inches. Neil says that this is a pretty good indicator of the relative efficacy against live targets of different projectiles and loads. In an email about this page, Neil wrote, "I'm not absolutely certain of its applicability to rifles (although it looks pretty good and is fine for slugs and rifles like .45/70). There are other factors at work above 2000-2500 feet per second. But every year that passes convinces me more that this is the perfect program for predicting handgun performance."

Sectional Density ("Sec. Dens." above) is defined as the weight (w) of the bullet in pounds divided by the square of its diameter (d) in inches: w/d^2 = pounds per square inch.

I used Remington ammo for the preset buttons only because the ballistics were easy to find on the web. I handload or use military surplus for most of my shooting. You can fairly easily change the <button> tags for your favorite loads.

billstclair.com/energy.html is the original version of this page, sized for a standard web browser.

You can store a local copy of this page on your iPhone by clicking here, and saving as a bookmark. Thanks to the data: URI kitchen.