9mm vs 10mm: Which One is Right for Me?

by Greg Rubenstein

Whether new to firearms or an expert – and everywhere in-between – all who choose to carry a gun for self-defense must make a decision about what to feed that weapon. Once you’ve decided carrying concealed is right for you, selecting the cartridge is perhaps the next most important choice.

Sure, you can pick which cartridge to use after narrowing down any number of other factors, but do so knowing the longer you put off settling on a cartridge, the more likely you are to end up changing things up down the road. Some might say that’s not necessarily a bad thing; afterall, firearms aren’t just for self defense.

Guns can be a hobby, a passion, and a way of life, and a big part of having fun with firearms is trying new things, comparing notes with buddies, and seeing if there’s something better than what you have today. Proficiency with your personal everyday carry (EDC) gear – including gun, ammo, holster, etc. – comes with practice, in particular repetition with the same equipment, so there is definitely a benefit to sticking with an EDC setup.

Which brings us back to cartridge. There is no one right answer (even for the same person), but the cartridge selected will inform every subsequent choice. From type of gun (semi-auto or revolver), to brand and model, holster, number of magazines to carry, or type of ammo, cartridge selection is a Big Deal.

Among all the options for EDC, 9mm (known formally as 9mm Luger, 9×19, or 9mm Parabellum) is an easy choice – proven, plentiful (even in times of shortages), and powerful enough. So if 9mm is good, then 10mm must be better, right? Well, maybe. Designed from the get-go for semi-automatic firearms, 10mm ammo can be had in loads appropriate for self-defense against any critter in North America: two-legged, four-legged, or even without legs. Thanks to the caliber’s recent renaissance, there are lots of choices in arms today, too, spanning every budget and action type.

To find out if 10mm really is right for you, a good place to start is with its much older, but smaller brother, the 9mm. If there is any one cartridge that is ubiquitous, it is the 9mm. You’d be hard-pressed to find a military or police force anywhere in the world which didn’t use 9mm in at least some of its arms. With the 9mm, you can be assured wherever you are, if there are only a few ammo choices available, one is almost certainly going to be 9mm.

Given its 120+ year history, the 9mm is also extremely well-developed, with a tremendous number and variety of loads, including light bullets at hyper-fast speeds, caliber-heavy bullets at either subsonic, standard, or elevated velocities, as well as an array of exotic and frangible bullets.

Guns chambering the 9mm are equally prolific, and can be had at a rock-bottom price, stratospheric expense, and everywhere in-between. Same goes for the variety of arms and action types available in 9mm: revolver, high-capacity revolver, single-stack semi-auto, or high- capacity semi-auto.

Then there’s design flexibility. Thanks to the cartridge’s tidy size, 9mm pistols can be specifically engineered for pocket-carry and to fit smaller hands. Many 9mm pistols today come with multiple grip panel options too, so the owner can customize one pistol to optimally fit a variety of hand sizes. Guns chambered in 9mm also offer more rounds than the same gun in a larger caliber, and crucially, 9mm handguns are generally very easy to shoot, thanks to the caliber’s
relatively light recoil.

If variety is the spice of life, then 9mm is spicy indeed. In addition to being able to find 9mm ammo just about anywhere – and at a price as low as any center-fire caliber – there are superb ammunition options in all the caliber’s main weights – 115 grain, 124 grain, and 147 grain – along with plus-pressure (P+) and beyond plus-pressure (+P+) loads. Specialty rounds also abound, with loads designed for optimal performance out of shorter barrels, low-flash rounds useful for preserving night vision, or frangible bullets for use in densely-populated areas, such as an apartment complex where you wouldn’t want your shot traversing yours and your neighbor’s walls.

Do your part and put the bullet into center-mass, and no matter which good-quality load you pick, you can count on the 9mm to perform as well as any other defensive round. Unless you have some specific reason to venture away from 9mm, it’s a good bet that this cartridge will deliver everything you need in a defensive round.

Yet the unending variety of 9mm pistols and loads is perhaps the 9mm’s biggest “fault” – so many choices with too many options; it’s ultimately impossible to know with certainty that any single 9mm pistol is the “best” option for you, since you’d have to wade through hundreds of examples just to narrow down to a single sub-type. If it’s possible to have too many choices, then that may be a central reason to go with something other than 9mm.

Which brings us then to the 10mm. Larger in every dimension, the 10mm is a formidable cartridge with tremendous performance potential. Serving up nearly twice the muzzle energy of the 9mm, 10mm is big and brash. Pistols chambering the 10mm cartridge are typically big guns, and have a much larger grip (to accommodate the cartridge’s longer overall length), while the barrel’s business end sports a gaping maw to spit out the 10mm’s .400-inch bullet, a significant up-sizing over the 9mm’s .355-inch bullet.

With all that power comes the need for even greater control. Loaded to its potential (or close to it), the 10mm cartridge is a handful, with lots of muzzle flash and flip. Rapid follow-up shots can be challenging, and with fewer rounds in reserve compared to a similar pistol chambered in 9mm, placement for each of those 10mm shots becomes even more important.

Finding 10mm ammo is often an exercise in futility, too. If you are lucky enough to locate some, your wallet is going to get socked, as the price of even full metal jacket “practice” loads is often double the cost of comparable 9mm ammo. Ouch.

For defensive use, full-power 10mm loads are often considered too powerful, with excessive penetration, noise, and muzzle flash. Down-loaded 10mm rounds are available, and these loads typically mirror 40 Smith & Wesson ballistics. Which begs the question, if one is going to use loads that mirror the 40 S&W, why not just use that cartridge? Why not indeed…

The 10mm is not without its advantages, however. It does offer tremendous flexibility, and if your intent is to hunt, or shoot targets, out to 100 yards, then the 10mm has loads appropriate for both uses. While the 9mm can certainly be used on targets at 100 yards, the point-of-aim at that distance requires holding about a foot over the target – a challenging task at best – while the 10mm can reach 100 yards with a much flatter-shooting trajectory. As far as hunting, doing so with a 9mm at long distances is not good practice, and potentially illegal (due to a lack of sufficient terminal ballistics).

There are situations where greater penetration is desirable – shooting through car doors, through walls (lots of walls) or through other barricades. These are specialized situations which likely aren’t encountered by the average citizen, but they do exist. Depending on where you live and what you do, and especially if you live in an area where bears might be encountered, you may even need the power provided by the 10mm (although if that is the case, a .44 Magnum might serve your needs even better!).

Finally, the 10mm has an undeniable cache. It’s a fun handful to shoot. Guns chambered in 10mm are big, and cool – see the Bren Ten (long out of production, but Sonny Crockett’s go-to Miami Vice pistol) or Glock 40, for just a couple of examples.

Concealed carry for personal protection is serious business, and selecting the cartridge most appropriate for you should be done with careful consideration and lots of personal testing. For most people, 9mm is a better choice than 10mm. But 10mm has its place. It’s all a matter of perspective, training, and individual need.