.40 S&W vs 10mm Auto

How do .40 S&W and 10mm Auto compare?

The .40 S&W and the 10mm Auto fire the same 0.400-inch bullet, but the .40 S&W case is 0.850 inches long against the 10mm's 0.992 inches, and its SAAMI maximum average pressure is 35,000 psi against 37,500 psi. The shorter overall length lets the .40 S&W fit pistols sized for 9mm, while the 10mm needs a larger frame. With the same 180-grain bullet, published 10mm loads range from close to .40 S&W velocity to roughly 275–325 fps faster.

The .40 S&W vs 10mm Auto page shows observed pricing for both alongside the specifications.

Where did the .40 S&W come from?

The 10mm Auto was introduced in 1983 for the Bren Ten pistol, with the cartridge designed by Norma. The FBI selected the 10mm after its 1987 wound-ballistics work, and a reduced-velocity "10mm Lite" load followed because full-power ammunition was more than many agents could control well. Smith & Wesson and Winchester then observed that the 10mm Lite's performance did not need the full 10mm case: a case shortened to about 22 mm could reach it. That shortened case became the .40 S&W in 1990, and because its overall length is close to 9mm's, it could be built into pistols with 9mm-sized grips.

The relationship explains most of the comparison. The .40 S&W was designed to reproduce a reduced 10mm load in a smaller gun; the 10mm retains the case volume for the higher-velocity loads the .40 S&W was never designed to match.

What do published loads show for velocity and energy?

Both cartridges are commonly loaded with 180-grain bullets, which makes a direct comparison possible. Velocities below are manufacturer-published; energy is computed as bullet weight (gr) × velocity² ÷ 450,240 and matches each maker's published figure within about one ft-lb.

Comparing like for like:

• FMJ practice loads: the two American Eagle loads are published 30 fps apart, and the 10mm load's computed energy is 6% higher (424 ÷ 400). At this tier the cartridges overlap.
• Hornady XTP loads: the 10mm load is published 325 fps faster than the .40 S&W load with the same bullet, and its computed energy is 1.80 times higher (650 ÷ 361).

The wider spread within 10mm — 245 fps between two 180-grain loads — is why the cartridge name alone does not identify a 10mm load's velocity. Published velocities come from manufacturer test barrels and will differ in other barrel lengths.

How does recoil compare?

Felt recoil depends on pistol weight, slide mass, and powder charge. What the published data supports is a bullet-momentum comparison: bullet weight (gr) × velocity (fps) ÷ 225,218, in pound-seconds. The pistol also receives momentum from the powder gas, which is omitted because factory boxes do not publish powder charges.

With the same bullet weight, momentum is proportional to velocity, so the ratios are easy to check: the faster 10mm load carries 1.34 times the momentum of the 950 fps .40 S&W load. Gun weight divides that impulse. A .40 S&W in a compact 9mm-sized frame and a 10mm in a full-size large frame can feel closer than the table suggests, because the 10mm pistol is heavier; the same 10mm load in a subcompact frame moves the gun faster.

Which pistols are chambered for each?

Glock illustrates the frame-size split clearly:

• .40 S&W: Glock 22 (full-size), Glock 23 (compact), and Glock 27 (subcompact) — the Glock 22 is the same frame size as the 9mm Glock 17.
• 10mm Auto: Glock 20 (full-size) and Glock 29 (subcompact), on the larger frame shared with the .45 ACP Glock 21.

Other makers follow the same pattern: .40 S&W models are usually built on the maker's 9mm-sized frame, and 10mm models on the maker's .45 ACP-sized frame (1911-pattern 10mm pistols such as the Colt Delta Elite are an example). Many .40 S&W pistols accept a factory or aftermarket barrel in .357 SIG, and some accept a 9mm conversion barrel and magazine. Some 10mm pistols accept an aftermarket .40 S&W conversion barrel.

The two rounds are not interchangeable in the same barrel. Both headspace on the case mouth, and a .40 S&W case is 0.142 inches too short to do so in a 10mm chamber. Firing any cartridge in a chamber not marked for it is outside the firearm manufacturer's specification.

What stays the same between the two?

Because both cartridges use the same 0.400-inch bullet, several properties are identical at a given bullet weight and depend only on velocity:

• Frontal area: 0.126 square inches before expansion, for every .40 S&W and 10mm bullet.
• Sectional density: weight (gr) ÷ 7,000 ÷ diameter². A 180-grain bullet computes to 0.161 in either cartridge, and a 155-grain bullet to 0.138.
• Bullet selection: many manufacturers load the same bullet designs in both cartridges, so a hollow-point design tested in one is often available in the other.

What changes is the velocity each case can deliver within its pressure limit, which in turn changes energy (with the square of velocity) and momentum (in direct proportion). The 10mm's additional 0.142 inches of case length provides powder space the .40 S&W lacks, and its SAAMI limit is 2,500 psi higher. Those two differences, not the bullet, account for the gap between the Hornady XTP loads in the table above.

The relationship also explains why .40 S&W loads cluster in a narrower velocity band than 10mm loads: the .40 was built to one performance target, while 10mm factory ammunition is loaded both to the reduced levels that inspired the .40 and to the cartridge's full pressure limit.

What is each cartridge commonly used for?

.40 S&W is commonly used for:

• Duty and personal-defense pistols, a role it held widely in U.S. law enforcement after 1990
• Practice and competition in 9mm-sized frames
• Pistols that can also be set up for .357 SIG or 9mm with a barrel change

10mm Auto is commonly used for:

• Handgun hunting of medium game where state rules allow handgun cartridges of this class
• Outdoor carry in areas with large animals, typically with heavy or hard-cast loads
• Shooters who want one pistol that can fire both lower-velocity practice loads and higher-velocity loads

Criteria a reader can apply:

1. Frame size. The .40 S&W fits 9mm-sized grips; the 10mm needs a .45-sized frame. Hand size and carry method determine which is workable.
2. Velocity tier. If the higher 10mm loads are not needed, the FMJ rows above show the two cartridges overlapping.
3. Conversion options. A .40 S&W pistol may also shoot .357 SIG or 9mm with the right parts; a 10mm may shoot .40 S&W with a conversion barrel.
4. Recoil tolerance. The momentum ratios scale with gun weight, so compare loads in the pistol actually being considered.

How does cost compare?

This article quotes no prices. Cost per round differs by load tier as much as by cartridge, because 10mm boxes range from practice FMJ to boutique full-power loads. Current observed figures are on the .40 S&W ammo prices and 10mm Auto ammo prices pages, and the trend over time on .40 S&W price history and 10mm Auto price history.

Related comparisons

• 9mm vs .40 S&W — Law-enforcement transition and capacity
• 9mm vs 10mm Auto — Use cases separated by energy
• .45 ACP vs 10mm Auto — Same frame size, different pressure

Related caliber pages

• .40 S&W ammo prices — Current pricing across tracked retailers
• .40 S&W price history — Observed trend over time
• 10mm Auto ammo prices — Current pricing across tracked retailers
• 10mm Auto price history — Observed trend over time

Sources

• SAAMI Cartridge & Chamber Drawings — Dimensions and maximum average pressure for .40 S&W and 10mm Auto
• C.I.P. TDCC tables — CIP maximum pressure for .40 S&W and 10mm Auto
• Federal Premium — American Eagle AE40R1 and AE10 published velocity and energy
• Hornady — Custom .40 S&W 180gr XTP (item 9136) and Custom 10mm Auto 180gr XTP (item 9126) published velocity and energy