When it comes to self-defense, many shooters hold to the belief that you should shoot the caliber that has the best ballistics and the most stopping power that you can handle. These shooters like to favor a larger caliber bullet, such as the 10mm Auto.

Other shooters believe that the ideal defense round should be lightweight and have low recoil, allowing for accurate and quick follow-up shots as modern jacketed hollow points (JHP) have made the caliber debate moot. These are typically your 9mm Luger concealed carry permit holders.

The 9mm vs 10mm caliber debate is an interesting one as these two handgun rounds are extremely different from each other, despite their bullet diameter only being separated by 1mm. And it begs the question, is bigger actually better when it comes to self-defense?

In this article, we will compare the 9mm Luger and the 10mm Auto under the auspices of determining which round will be the better choice for personal defense.

What’s the Difference Between 9mm and 10mm?

When new shooters first hear about the 9mm Luger and the 10mm Auto, they often think that they are very similar cartridges. I mean how much difference can 1mm make?

Well, the answer is: Quite A Bit!

Sure, the bullet diameter is only 1mm different, but the bullet weight, muzzle velocity, and ft-lbs of energy are considerably different when comparing 10mm vs 9mm.

So, when you’re loading up your favorite semi-auto, which one do you go for? Do you go for your trusty Glock 19 or is a Glock 20 your go-to personal defense handgun?

In the next few sections, we will break down the differences between the 10mm Auto and the 9mm Luger to give you a better idea of which handgun caliber will be best for your needs.

Case Specs

Looking at the case spec chart, we see that the 9mm Luger and the 10mm Auto are extremely different.

The first thing to note is that the 10mm fires a 40-caliber bullet (0.401” bullet diameter) while the 9mm Luger fires a smaller, 9mm bullet (0.355” bullet diameter). Furthermore, the case capacity of the 10mm round is just short of double that of the 9mm, meaning that more gunpowder can fit into the 10mm allowing it to fire heavier bullets at a higher muzzle velocity.