9mm Self Defense Ammo Energy Comparison
In any given discussion of self defense/personal protection ammo there are a number of specifications that will almost always come up: caliber, bullet style, velocity, penetration, and expansion. A less often discuss specification is energy.
A bullet's energy is determined through the use of a fairly straight forward calculation that considers the bullet's weight and its speed. Here is a Wikipedia article on the specifics of the formula for those of you who are interested. For the rest of us, Googling "Bullet Energy Calculator" will produce easy-to-use tools.
Since a round's energy depends partially on its speed, the same round will carry different amounts of energy along its flight path as well as at the muzzle of different length barrels. Generally, the longer the barrel, the faster a bullet will fly and the more energy it will carry. This is why some people prefer "Plus P" loads for their compact and subcompact pistols.
If the same round can carry different amounts of energy how do ammunition manufacturers measure and list their ammo's energy? The short answer is that each one does it a little differently. The status quo for manufacturers measuring their products energy is at the muzzle of a 4 or 5-inch pistol. Additionally, they often use very popular pistols like Glock 17s or Sig Sauer 226s for these tests. This is one of the reasons why everyone says you need to shoot "Ammo X" in your own gun before you rely on it. There is no way to know for sure how it will perform in your weapon, with your grip, in real life until you shoot it exactly like that.
To be clear, energy isn't necessarily the most important attribute of ammunition performance but it does deserve consideration. After all, your super fancy plastic tipped hollow point won't be very effective on target if it has dumped all its energy before it gets there. Below is a chart of the energy rating of a handful of the most popular 9mm self defense rounds available today. Hopefully this will add some additional insight into your next "Best Defense Ammo" conversation.
The green bars are rounds we carry (links are belwo), the rest are pretty easy to find online or at your local store.