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I first started learning about handguns before the advent of the internet. Today, everything you could want to know is at your fingertips. Back then, if you wanted to learn more about shooting, it was best to hang out at the local gun shop and ask questions. One day, my friend behind the counter passed me an ammunition catalogue and asked me if I knew how to read ballistics tables. I had to admit that I had no idea what he was talking about. What he taught me that day started me on a path of understanding that has helped me time and again to determine which caliber was right for my needs.
When people talk about which caliber is the best, they are actually discussing ammunition performance. Does the ammunition do the job I want it to? How does this caliber compare to other rounds on the market? Knowing that I wasn't ready for all the intricacies that the study of ballistics entails, my friend started me off with a simple table:
|Cartridge||Bullet Weight||Velocity (fps)||Energy (ft.lbs)|
|Muzzle||50 Yards||Muzzle||50 Yards|
|.25 ACP||35 grn||900||813||63||51|
|9 mm||115 grn||1200||1074||336||269|
|.38 Special||158 grn||800||765||225||205|
|.357 Magnum||158 grn||1250||1134||548||451|
|.45 ACP||230 grn||900||859||412||377|
|.44 Magnum||240 grn||1760||1380||1650||1015|
Tables like this one describe cartridges and three aspects of the bullet: the bullet's size, how fast it travels, and how hard it hits the target. This information can be used to understand ammunition’s performance and how it compares to other rounds. Tables like this are read from left to right.
The first two columns tell us about the bullet's size (diameter and weight). The first column shows the name of the cartridge, which usually includes the approximate diameter of the bullet in hundredths of an inch, also known as "caliber" (.45 ACP), or in millimeters (9MM). The bigger this number is, the larger the bullet's diameter. The second column shows the bullet’s weight measured in grains. All you really need to know about grains is that 437.5 of them equal an ounce. The larger the number of grains is, the heavier the bullet.
The third column tells us how fast the bullet travels. In the United States, bullet velocity is represented in feet-per-second (fps). This column is usually split into two or more sections to show how the velocity decreases with distance. Muzzle velocity is measured as close to the tip of the gun's barrel as possible. The bullet will be traveling at its highest velocity as it leaves the barrel. It loses speed the farther it travels. Just as a point of reference on velocity, an object breaks the sound barrier at around 1100 fps. That’s one of the reasons some calibers are louder than others. If the bullet is traveling faster than 1100 fps, it creates a sonic boom.
The last column shows how hard a bullet strikes the target. The amount of impact energy is represented in foot-pounds (ft-lb). Figuring out the foot-pounds exerted by a bullet is where the math gets complicated. Rather than try to work it all out on my own, I choose to trust the experts who write the tables. However, the results of these calculations are easy to read. The larger the number of foot-pounds is, the harder the bullet strikes. As the bullet travels away from the gun, and as it loses velocity, it also loses impact energy. Most tables will show you the bullet’s energy at the muzzle and then add more columns to show how the energy decreases over distance.
Now that all of these technical definitions are in place, it’s not so hard to do a basic side-by-side caliber comparison. The following examples will give you a few rules of thumb to help you start applying what you’ve learned so far:
The .45 ACP and the .25 Auto both have the same muzzle velocity (900 fps), but the .45 hits the target with 412 ft-lbs of energy compared to the .25's 63 ft-lbs. This is because it takes more energy to get the .45’s 230 grains of lead (more than ½ an ounce) to travel at 900 fps than the .25’s 35 grains (less than 1/10 of an ounce), and as a result, the .45 has more energy to deliver when it strikes.
Rule of Thumb: When velocities are equal, the heavier bullet hits harder.
Which two rounds in the chart have the same bullet weight? The answer is the .38 Special and the .357 Magnum. In this particular case, they both happen to have same diameter as well. Yes, I know, it’s called a .38 Special, but the actual bullet diameter is .357, just like the .357 Magnum (don’t ask me why they called it a .38). However, the .357 Magnum contains a more powerful powder charge than the .38 Special. This increase in power causes the.357 Magnum bullets to travel at a higher velocity, resulting in 548 ft-lbs of strike energy compared to the .38 Special's 225 ft-lbs.
Rule of Thumb: When bullet sizes are equal, the faster bullet hits harder.
Which cartridge contains the largest bullet? Based on the cartridge names, the .45 ACP does. However, take a look at the .44 Magnum. It has a slightly smaller bullet diameter, but the bullet weighs about 10 grains more than the .45 ACP. Not only that, the .44 Magnum cartridge yields a whopping 1650 ft-lbs of energy at the muzzle. This dwarfs every other round in the table, including the .45 ACP. So, the .45 is the second most powerful cartridge, right? Actually, it’s the .357 Magnum because of its greater velocity.
Rule of Thumb: When it comes to performance, bullet diameter alone will not tell you how powerful a cartridge is. You also need to consider the bullet velocity and weight.
Now you have just enough information to begin reading the ballistics tables the ammunition companies are kind enough to provide. However, this article is only meant to be an ice breaker on the topic of pistol ballistics. Run an internet search on "handgun ballistics" and you will find there is so much more to learn.
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