10mm vs 357 Magnum

Banana Ballistics • August 01, 2023

So, you’re tired of that boring old 9mm and want to get into something a bit more powerful? Perhaps you have been debating between the 357 magnum and the 10mm Auto and just can’t decide which one is right for you. Considering how different these cartridges are, this can be a tough decision so we will be going over the benefits of each to help make your decision a little easier.

Physical Attributes

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Let’s get one thing out of the way……. Other than having a brass case and firing a projectile, the 10mm and the 357 magnum could not be further apart in terms of design. Stood side by side, the first thing you may notice is the large difference in height between the 357 magnum and the 10mm.

An empty 357 magnum case stands at a nominal length of 1.29 inches while an empty 10mm case only stands at a nominal length of 0.992 inches. With over a quarter-inch difference in height, it would be easy to assume that the 10mm has less case capacity than the 357 magnum. Although this assumption is correct, the difference in capacity may not be as large as you would think.

The 10mm, with its wider case, has a capacity of approximately* 24.1 grains of H2O. Although the 357 magnum case towers over the 10mm, its much narrower case explains why its capacity is only marginally larger, at approximately* 26.2 grains of H2O.

Other than height, another notable difference is the diameter of the projectiles being used in each cartridge. As the name suggests, the 357 magnum is using 0.357-inch diameter projectiles (many cartridges do not use the exact diameter as the naming). Although the 10mm is a metric name, it is using much wider 40 caliber bullets, 0.400-inch in diameter.

Due to its wider diameter, the 10mm is able to fire heavier projectiles than the 357 magnum, though the difference may not be as large as you would think. 40 caliber projectiles typically range in weight between 120 grains to 220 grains whereas 357 caliber projectiles typically vary from 90 grains to 200 grains. Bullets seldom fall outside of these ranges; however, ultra-light offerings from companies such as Liberty Defense do exist for both cartridges.

The last difference we will discuss is the case design of each. Designed to be fired out of semi-automatic handguns, the 10mm case utilizes a rimless design. Unlike the 10mm, the 357 magnum was designed to be fired out of revolvers, which is evident in its rimmed design. Due to the difference in case diameters, 10mm cases almost always utilize large pistol primer pockets, whereas 357 magnum cases are limited to small pistol primer pockets.

Platforms

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Perhaps the biggest question you have to answer when choosing between the 10mm and the 357 magnum, is whether a semi-auto handgun or a revolver fits your needs better. The 10mm is primarily chambered in semi-auto handguns, whereas the 357 magnum is generally chambered in revolvers. Although there are revolvers chambered in 10mm and semi-auto 357 magnums, these are few and far between.

Because of the difference in platforms, capacity is usually quite different between the 357 magnum and the 10mm. Standard 357 magnum revolvers typically hold 6 rounds of ammo, but modern offerings such as the Smith and Wesson R8, can hold up to 8 rounds. Although this is a substantial capacity for a centerfire revolver, it does not come close to the capacity of many 10mm semi-auto offerings.

With a magazine capacity of 15 rounds plus 1 round in the chamber, the most common 10mm handgun on the market, the Glock 20, doubles the capacity of an 8-round 357 magnum revolver. Glock users also have the option of using up to 30-round detachable magazines, which doubles the already large capacity of 15 rounds. This means that a Glock 20 has the potential to hold 31 total rounds of ammo, which is a monstrous amount of ammo for such a powerful cartridge.

If polymer frame double stacks do not suit your fancy, a single stack 1911 is another popular choice for the 10mm. The downside of a single-stack magazine, however, is the drop off in capacity. Many single stack 1911s only hold 8+1 rounds of 10mm, or 1 more round than an 8-shot 357 magnum revolver.

The other thing to consider when deciding between platforms is reload speed. Because semi-auto handguns use detachable magazines, reloads can be done in a matter of seconds (assuming magazines are pre-loaded). This is not to say that revolvers are slow, as speed loaders can be used to fill a cylinder in quick order. Unlike semi-autos, however, revolvers do not dispense used cases once shot. These spent cases must be emptied after the final shot has been fired, which adds time to the process of reloading a revolver.

Power

According to SAAMI, the 357 magnum has a maximum pressure rating of 35,000 psi, whereas the 10mm has a maximum pressure rating of 37,500 psi. With this 2,500-psi increase in maximum pressure, it would be easy to think that the 10mm can produce more kinetic energy than the 357 magnum, though this is not typically the case.

While both cartridges produce around 500-600 ft/lbs. of energy at the muzzle with standard load offerings, they differ greatly when it comes to max loads**. If we look at Buffalo Bore’s 180 gr hollow point offering in 10mm, we see that it produces 728 ft/lbs. of energy at a muzzle velocity of 1350 feet per second. This is a substantial amount of kinetic energy for a semi-auto handgun but looking at Buffalo Bore’s 180 gr XTP offering in 357 magnum, we see that it is producing 899 ft/lbs. of energy at a muzzle velocity of 1500 feet per second.

At the muzzle, this 357 magnum load produces 171 ft/lbs. more than the 10mm with the same bullet weight. This is almost a 23 percent jump in muzzle energy, but it should be noted that Buffalo Bore rated the 357 magnum in a 6-inch barrel, whereas the 10mm was rated in a 5-inch barrel. The 10mm would likely gain velocity in a 6-inch barrel, though it would have a hard time matching this 357 magnum load.

This is not to say that the 10mm is a slouch by any means, as it is producing a considerable amount of kinetic energy for a semi-auto handgun. Another thing to consider is that depending on the weight of the handgun, the extra muzzle energy produced by the 357 magnum can result in more recoil. To help compensate for this, the 357 magnum does have a trick up its sleeve……. The ability to shoot 38 special out of the same revolver.

That’s right, if your wrists get tired, or you want to practice without the extra recoil of the 357 magnum, you have the ability to shoot 38 special out of the same revolver. While the 38 special may not be impressive in terms of kinetic energy, its low pressure and muzzle velocity equates to very light recoil (especially out of full-size 357 magnum revolvers). Unlike 357 magnum revolvers, semi-auto 10mm handguns can only chamber one cartridge safely.

**Always ensure the ammo you’re using is rated for your specific firearm.

10mm or 357 Magnum?

Now comes the tough part, deciding whether you want a 10mm or a 357 magnum.

Although the 10mm may not be able to produce quite as much kinetic energy as maximum 357 magnum loads, it comes very close while offering some major benefits. Perhaps the greatest advantage of the 10mm is the platform that it was designed for. Having the ability to fit 15 full-power 10mm loads into a standard magazine is hard to pass up. If that isn’t enough power for you, then you have the option of increasing this capacity up to 30 rounds with extended mags. That is a lot of firepower!

If capacity is not high on your list, the 357 magnum is a powerful option capable of generating some serious velocities with light bullets. Extra muzzle energy is nice, but you may not want to deal with the recoil of the 357 magnum all the time. Having the ability to fire much cheaper and much lower recoil 38 special loads out of the same revolver is a key selling point for many. 

Regardless of which cartridge you choose, the 10mm and the 357 magnum are both great options that do not show any signs of slowing down in popularity.

*The case capacities listed represent the approximate amount of H2O that will fit inside an empty case. These values can vary based on the manufacturer as different companies will typically result in slightly different case capacities.

--Banana Ballistics