I own both 9mm and 10mm pistols. I’ve shot thousands of rounds in both calibers.
A 9mm fires a .357 bullet ranging from 115 to 147 grains with up to 450 ft/lbs. of muzzle energy. The 10mm fires a .40 bullet weighing 180-230 grains with energies up to 700 ft/lbs. 10mm has noticeably more recoil. 9mm is good for protection while 10mm can be used for hunting.
Both of these cartridges are useful for defense, but there are certain instances where one is better than the other. I’ll go over the weaknesses and strengths of both, and give recommendations on what you should get.
What’s the Difference Between 9mm and 10mm Pistols?
The 9mm has several last names. It can be listed as 9mm Luger, 9mm Parabellum, and 9×19. They are all the same thing. Over the years, different countries have given the cartridge different designations. These are all interchangeable, but there are many other 9mm cartridges that are not. If it has any other name than these, it’s not “the 9mm”.
There is a huge chasm of difference between these two cartridges. The 9mm is a “good enough for most uses” option, but certainly not a high-power pistol round. 10mm is higher pressure, higher energy round that has more uses than the 9mm.
9mm was designed in 1901 and it’s hardly changed since then. It generally fires a 115-grain bullet going 1200 fps or a 124-grain bullet going around 1100 fps. Most 9mm bullets are sharply rounded, almost pointed. That’s required for the bullet to reliably feed in all the various models, including the antiques.
10mm, also called 10mm AUTO was developed in the ’80s as an FBI field agent gun that would pack nearly .357 Magnum power in a semi-auto pistol. It worked, although the FBI ended up going with the 40 S&W, then the 9mm that they use today.
The 10mm is a bridge between standard pistols cartridges and the magnum pistol cartridges. Everything below 10mm is in the “lesser” category. Everything above the 10mm is in the more powerful category and generally has a “Magnum” in the name to sell the point.
How Much More Powerful is a 10mm than a 9mm?
The 10mm averages 51.4 % more power than the 9mm. 9mm handguns create an average of 350 ft/lbs. of energy, while 10mm handguns create an average of 530 ft/lbs. of energy. 9mm +P reaches 450 ft/lbs., while full power 10mm reaches over 700 ft/lbs. or energy.
Let’s put that into perspective. 2 rounds of 10mm have about as much energy as 3 rounds of 9mm. It may not sound like much when put like that, but it is ballistically significant. Every shot from 10mm is sort of like getting hit by one and a half rounds of 9mm.
Let’s pitch these two cartridges up with a few more sets of numbers. The 9mm is .357 caliber (diameter) with a circumference of 1.12”. ta 10mm is .400 caliber with a circumference of 1.24”. That may not seem like much. The caliber is only .043 inches different. Does that really matter? Yes, it does.
A bigger difference is seen in the circumference. That’s a .130 difference. Not only does that allow for a heavier bullet, but the circumference adds more wounding area. A bullet’s power can be summed up in how much tissue it destroys. In this case, about 11 percent more.
A pistol bullet only the tissue that directly touches the bullet. Thus, the wider the bullet, the more tissue will be destroyed. The larger diameter of the 10mm reduces the time it takes for a well-placed shot to cause a devastating loss of blood.
Because the 10mm is not only bigger but penetrates further than the 9mm, it is significantly more powerful and can destroy significantly more tissue.
In terms of penetration, the 10mm wins over the 9mm every day. The 10mm is slightly wider, but also much faster and heavier. The average 9mm bullet is 124 grains and the average 10mm bullet is 180 grains. That’s a 45% gain in bullet weight over the 9mm.
The average velocity of a 9mm round is 1,100 fps while the average velocity of a 10mm round is 1,200 fps. That’s a 10% increase in velocity. Now let’s see what measurable gains new can see in 10mm from the 9mm.
11% wider destroyed tissue area, 45% more bullet weight, and 10 percent more velocity. I’m no mathematician, but that certainly equals more power and penetration than the 9mm.
The 10mm AUTO penetrates about 20 percent more than a comparable load in 9mm and creates up to twice the vascular damage. That’s a significant difference.
9mm vs 10mm for bear defense
A 9mm pistol isn’t adequate for bear defense. 10mm AUTO is much more adequate and is considered the minimum pistol for bear defense. The 10mm will penetrate more than 9mm, and will create a much larger wound on a though skinned bear.
Hang around the gun store long enough and you’ll hear someone talk about a “bear gun”. They usually mean a pistol carried in the woods for fending off an angry bear. Traditionary the ideal handgun was a large revolver, but nowadays semi-auto pistols are nearly as common.
I do know some people who carry a 9mm for defense in bear country. There are some awesome stories about mad grizzlies being felled with the little 9mm. I certainly can’t recommend it though. the 9mm is a mid-power pistol round that just doesn’t bust holes like something bigger would.
A 9mm can have up to 3 feet of penetration in soft tissue, but bears aren’t all soft tissue. They have a tough hide full of thick course fur, a layer of soft fat, then dense muscle and heavy bones. The 9mm will penetrate to the vitals in a bear under perfect conditions, but is prone to failure.
Even the most powerful 9mm loads lack the power needed to shatter the heavy shoulder or to penetrate deep enough from a less fair shot angle. In a bear attack, you don’t have time to wait for a perfect shot and have to take what you can get.
Plus, the .357 bullet traveling at around 1200 fps fails to create a wide enough wound to cause a bear to quickly bleed out. 9mm hollow points are useless against bears because they often penetrate only 6 inches into a bear’s tough side. Those who carry a 9mm for bears load up with heavy fmj or hardcast ammo.
9mm handguns are not suitable for bear protection, but the 10mm is. 9mm bullets lack the power and wounding capabilities to reliably bring down a bear. 10mm is the minimum handgun cartridge that should be carried for bear defense.
Is 9mm better than 10mm for Concealed Cary?
Both 9mm and 10mm are good choices for Concealed carry. The 9mm and 10mm have about the same success rate for personal defense. The 10mm will handle some situations the 9mm will not because it is more powerful. 10mm pistols are harder to conceal than 9mm. Both have similar magazine capacities.
Saying one is better than another can sometimes be a tough call. It often boils down to personal preference, what you have, or what’s available locally. Even though t’s more common now than ever, you may not be able to find 10mm ammo at your local store and that certainly can influence your buying decision.
Almost every law enforcement agency in the US, and US military has decided that 9mm is plenty enough for their needs. It really comes down to what you can get, and what you can shoot well. I always recommend choosing the most powerful pistol you can both conceal and shoot accurately.
9mm vs 10mm for Home Defense
Both 10mm and 9mm are adequate for home defense. The best choice is whichever you can shoot accurately and quickly. 10mm has more power, but slightly less capacity. 9mm tends to be more manageable for most shooters. Both have similar over-penetration concerns for home defense.
For home defense, the weight and size of a pistol aren’t a concern. In fact, a heavy pistol is nice because it helps to mitigate recoil. I advocate the biggest gun you can functionally and adequately handle. I have my 10mm nearby at home, and my wife has her 9mm within reach.
Personally, I don’t actually like pistols for anything defensive. Compared to a long gun, a pistol is very weak and incredibly inaccurate. They are a compromise. We compromise comfort and concealability for a less powerful and harder-to-aim option.
I prefer my 12-gauge shotgun loaded with birdshot as a dedicated home defense gun. It’s powerful at the short ranges in my home (20 feet max) and doesn’t penetrate too much. It lessens the danger of overpenetration in my trailer house. That’s my .02 cents.
10mm vs 9mm +P
10mm ammo is more powerful than the hottest loaded 9mm +P rounds. 9mm +P is around 20 percent less powerful than standard 10mm AUTO loads, and 40 percent less powerful than full-power 10mm Auto loads. 9mm +P is significantly lower power than decent 10mm ammo.
Is 10mm too powerful for self-defense?
10mm is not too powerful for self-defense. The recoil is comfortable for most shooters and most 10mm defensive ammo passes the FBI handgun ammo test for penetration and wounding capabilities. Both 10mm and 9mm may over-penetrate but the 10mm is more prone to it.
It comes down to your personal preference and specific situation. If over penetration may be a concern for you, you could consider the 9mm, which will penetrate a bit less. Good 10mm defensive ammo should not pose too much additional risk, but it’s still more risk of overpenetration. Weigh your risks.
Can You fire 9mm in a 10mm pistol?
9mm ammo will not fire in a 10mm pistol. It may load into the chamber, but should not fire. The case dimensions on a 9mm will cause it to be too far forward in a 10mm chamber to properly engage the firing pin. Firing 9mm in a 10mm pistol is a bad idea.
This is a case of “just because it fits doesn’t mean that it should”. There are times when people in desperation try the wrong caliber of ammo in an emergency. In wartime, people have fired any bullet they could cram into the chamber of their gun.
I just loaded several 9mm rounds in my 10mm magazine. The ammo hand-cycled through my Glock surprisingly well, but they wouldn’t fire. The 10mm holds mm ammo too far forward for a proper firing pin hit. The rim is thicker on the 10mm than the 9mm, which allows it to handle higher pressures.
According to my test, and my books of cartridge measurements, it ain’t gonna work. But let’s say it would fire. Would it be safe? I assume it surely would be safe. 9mm is lower pressure and will be much lower pressure in the larger 10mm chamber. The bullet will just wobble down the barrel. In fact, the entire 9mm cartridge can slide down the barrel of a 10mm AUTO.
