01 / At a glance
The basics
- Origin
- United States
- Introduced
- 1983
- Ignition
- Centerfire
- Case form
- Rimless, straight-walled
- Diameter
- 10.2 mm
- Case length
- 25.2 mm
Rounded values to help you identify the cartridge, not manufacturing drawings. See the cited standard for exact dimensions and tolerances.
Do not mix it up
The 10mm Auto and .40 S&W use the same bullet diameter, but the 10mm case is longer and runs at higher pressure. A 10mm pistol can fire .40 S&W in some cases, but a .40 pistol must never fire 10mm.
The 10mm Auto is a powerful semi-automatic pistol cartridge that fires a .400 inch bullet, usually 135 to 220 grains, at speeds from about 1,000 to well over 1,300 ft/s. It carries more energy than the 9mm Luger, the .40 S&W and the .45 ACP, and it is the strongest pistol cartridge in common use for autoloaders. It has a loyal following among hunters, hikers in bear country and shooters who want a lot of power in a magazine-fed pistol.
This guide explains what the cartridge is, how it performs, how to choose ammunition and a pistol, and how it compares with the 9mm Luger, .40 S&W, .45 ACP and .44 Magnum. It is a reference page, not a loading manual, and it contains no handloading data.
A short history
The 10mm Auto came out of the ideas of Jeff Cooper, a firearms instructor and writer who wanted a flat-shooting, powerful pistol cartridge with a medium bullet. The cartridge was developed in the early 1980s, and it was introduced in 1983 with the Bren Ten pistol, made by Dornaus & Dixon. Norma loaded the first ammunition.
The Bren Ten company ran into financial trouble, and the pistol was out of production by 1986. The 10mm Auto survived because Colt chambered its Delta Elite 1911 for it in 1987, and Smith & Wesson and Glock followed. Glock introduced the Glock 20, a large-capacity pistol, in 1990.
The FBI became interested after a 1986 shootout in Miami, in which agents were killed by suspects who took many hits before they stopped. The FBI tested the 10mm and adopted a version of it, but many agents found the full-power load too hard to control, and the Bureau moved to a reduced-power load. Smith & Wesson and Winchester then shortened the cartridge to fit a smaller pistol, which became the .40 S&W in 1990. The 10mm survived as an enthusiast cartridge, and today it is more popular than it has been in decades.
Why it is so popular
The first reason is power. A hot 180 grain load at 1,250 ft/s carries around 620 foot-pounds, and a 200 grain hard-cast bullet at 1,200 ft/s has deep penetration. That is a lot more than a 9mm Luger gives, and it comes in a pistol that holds 15 rounds or more.
The second reason is the range of loads. The cartridge can be loaded to mild levels, close to the .40 S&W, or to hunting levels. Shooters can buy gentle practice ammunition and full-power ammunition for the field.
The third reason is the guns. Glock, Smith & Wesson, Sig Sauer, Springfield, Colt and others make 10mm pistols, and revolvers and carbines are made for it too. There is a lot of choice, and prices are fair.
Specifications at a glance
| Specification | Value |
|---|---|
| Bullet diameter | .400 in (10.2 mm) |
| Case length | 0.992 in (25.2 mm) |
| Maximum overall length (SAAMI) | 1.260 in (32.0 mm) |
| Case type | Rimless, straight-walled |
| Primer | Small pistol (large pistol in some loads) |
| Maximum average pressure (SAAMI) | 37,500 psi |
| Typical bullet weights | 135 to 220 grains; 180 and 200 grains are most common |
| Typical muzzle velocity | About 1,030 ft/s for a standard 180 grain load; hot loads reach 1,200 ft/s or more |
| Common barrel twist | Varies by maker |
Values are rounded for reference. Exact dimensions and tolerances are in the SAAMI and C.I.P. standards cited at the end of this page.
Strengths and limits
The 10mm Auto is a compromise between a 9mm and a magnum revolver. It has the features of both and the full strengths of neither.
| Advantage | Limitation |
|---|---|
| More energy than the 9mm, .40 S&W and .45 ACP | More recoil and more blast than those cartridges |
| Flat trajectory for a pistol cartridge | Ammunition costs more and has fewer choices |
| High capacity in modern pistols | Larger, heavier pistols than a 9mm |
| Good penetration with hard-cast bullets | Standard-weight loads sold today are often weaker than the original |
| Wide range of loads from mild to hot | Can be hard on small hands and on the pistol itself |
The 10mm is not a magnum revolver cartridge. A .44 Magnum has a heavier bullet and more energy, and a revolver is built stronger. What the 10mm offers is a high-capacity pistol with real power. For most people, the right way to use it is as a field gun or a woods gun, and not as a gun to carry in a crowd.
Loads vary a great deal
Two boxes marked 10mm Auto can be very different. Some are close to the .40 S&W, and others are close to the original 1980s load or hotter. Read the velocity and bullet weight on the box. A pistol that feeds and shoots one reliably may not like another.
Ballistics
The tables and charts below show one common factory load, a 180 grain full metal jacket at 1,030 ft/s, fired from a pistol zeroed at 25 yards.
| Range (yd) | Velocity (ft/s) | Energy (ft-lb) | Drop (in) | Wind drift, 10 mph (in) |
|---|---|---|---|---|
| 25 | 998 | 398 | 0 | 0.2 |
| 50 | 970 | 376 | -1.3 | 0.8 |
| 75 | 944 | 356 | -4.9 | 1.8 |
| 100 | 921 | 339 | -10.9 | 3.1 |
Reading the numbers
From a 25-yard zero the bullet is within about an inch and a half of the point of aim at 50 yards and falls about 11 inches at 100 yards. A 10 mph crosswind moves it about 3 inches at 100 yards. Energy falls from about 424 foot-pounds at the muzzle to about 339 at 100 yards.
This is a standard-velocity load. Hunting and defense loads in 10mm are much hotter. A 180 grain bullet at 1,250 ft/s has about 625 foot-pounds at the muzzle and a flatter path, and a 200 grain hard-cast bullet at 1,200 ft/s gives deep penetration.
How these figures were made: the muzzle velocity (1,030 ft/s) and weight (180 grains) are published figures for the Federal American Eagle 180 grain FMJ load. The ballistic coefficient (G1 0.174) was fitted to match the published downrange velocities. Drop, velocity, energy and wind drift are computed with a standard point-mass model, a 25-yard zero, a 0.9 inch sight height and standard atmosphere. They are estimates. Velocity depends on barrel length, and loads from different makers vary a lot.
Recoil and shooter comfort
The 10mm Auto kicks harder than the 9mm Luger, the .40 S&W and the .45 ACP, and the difference grows with hot loads. The recoil is sharp rather than heavy, and a full-size pistol with a good grip takes much of it away. Compact pistols are harsh with full-power ammunition.
Start with mild factory loads, close to .40 S&W power, and move up as your technique improves. A tight, high grip and a stable stance matter more than with a 9mm. Muzzle blast and flash are significant with hot loads, so wear hearing protection, and think about how you will see in low light.
How to choose ammunition
Choose by purpose first, then velocity. The same 10mm Auto name covers very different products.
| Load type | Best for | Notes |
|---|---|---|
| Full metal jacket, 180 to 200 grains | Practice and range use | Cheapest; often a standard velocity |
| Jacketed hollow point, 155 to 200 grains | Defense and general hunting | Designed to expand; many velocity levels |
| Hard-cast lead flat point, 180 to 220 grains | Large game, defense in bear country | Deep penetration; check that your gun allows lead |
| Reduced-power or "lite" loads | Practice and comfort | Close to .40 S&W power |
| Light, fast bullets, 135 to 155 grains | Fast loads and small game | High velocity, less penetration |
Bullet weight and velocity
A 180 grain bullet at standard speed is a good, mild choice. A 200 grain bullet at 1,150 to 1,250 ft/s is a typical hunting choice, and a 200 to 220 grain hard-cast bullet is used for deep penetration. Light bullets are fast but give up penetration. Pick the load that feeds reliably and hits where you aim.
Strong loads need a strong pistol
Full-power loads wear a pistol faster. Some small or light pistols are not built for continuous use of hot ammunition. Use the loads the maker recommends, and replace the recoil spring on the schedule the maker gives.
How to choose a pistol
The best pistol is the one you can shoot accurately and use for the job you have in mind. These are the points that matter most.
- Size and weight. Full-size pistols such as the Glock 20, Smith & Wesson 1006 or Springfield 1911 tame the recoil. Compact models are lighter to carry but harder to shoot.
- Capacity. Many 10mm pistols hold 15 rounds or more. Single-stack 1911s hold 8 or fewer.
- Barrel length. Four and a half to six inches is the usual range. Longer barrels add velocity and a longer sight radius. A threaded or compensated barrel helps with recoil.
- Controls and sights. Choose a trigger and grip that suit your hand. Adjustable or night sights are useful for field use, and many pistols accept a red dot.
- Holster. For field carry, a chest holster is more comfortable and quicker than a belt holster for many hikers.
Revolvers and carbines
Smith & Wesson makes 10mm revolvers, and carbines in 10mm exist, including models that use Glock magazines. A carbine increases velocity and accuracy and makes the cartridge easier to use at 100 yards and more.
Zeroing and practice
Many pistols are set to hit the point of aim at about 25 yards. For hunting, a 50-yard zero is common, because the path stays within a few inches out to 75 yards. Test your pistol with the ammunition you plan to use, shoot a group from a rest and adjust the sights if the group is off. Different bullet weights and velocities hit at different points.
Practice with mild loads for most of your sessions and finish with a few full-power rounds. Dry-fire at home with an unloaded pistol and a safe direction to build smooth trigger control. Regular practice is worth more than a single long session.
Practical uses
Defense in bear country
Many hikers and anglers carry a 10mm pistol with hard-cast bullets in bear country. The pistol holds more rounds than a revolver, and the cartridge has good penetration. Bear spray is the first choice of most people, and it has a good record. A pistol is a last resort, and the shooter needs to practice enough to hit under stress.
Handgun hunting
With a well-built bullet of 180 to 220 grains, the 10mm is used on deer, hogs and similar game at close range, usually inside 50 yards. Some jurisdictions set minimum caliber or energy rules for deer that a 10mm may not meet, so check the rules for minimum caliber, energy and barrel length.
Sport shooting
The 10mm has a presence in action pistol and steel shooting, mostly with mild loads. It is a fun cartridge on the range, and the flat path makes steel at 50 yards easy to hit.
Personal defense
The 10mm is used for defense, although it is bigger and kicks more than most defensive pistols. Many people choose a 9mm for this because it is easier to shoot well. Laws on carrying and using firearms for protection vary, so follow local laws and get training.
10mm Auto vs similar pistol cartridges
The table lists the pistol cartridges most often compared with the 10mm Auto. Figures are rounded and use the SAAMI maximum average pressure.
| Cartridge | Bullet diameter | Case length | Max pressure | Typical use |
|---|---|---|---|---|
| 10mm Auto | .400 in | 0.992 in | 37,500 psi | Hunting and field pistols |
| .40 S&W | .400 in | 0.850 in | 35,000 psi | Duty and defense pistols |
| 9mm Luger | .355 in | 0.754 in | 35,000 psi | All-round pistol and carbine |
| .45 ACP | .452 in | 0.898 in | 21,000 psi | Large-bore pistols and competition |
| .357 SIG | .355 in | 0.865 in | 40,000 psi | Duty pistols |
| .44 Magnum | .429 in | 1.285 in | 36,000 psi | Hunting revolvers |
Against the .40 S&W, the 10mm uses the same bullet but has a longer case and more power. Against the 9mm Luger, it has a heavier bullet and far more energy, and less capacity and more recoil. Against the .45 ACP, it is faster and flatter, with a smaller bullet and higher pressure. Against the .44 Magnum, it has less energy but more capacity and a smaller gun.
Care and storage
Clean the barrel, slide rails and feed ramp after each range session, and oil the moving parts. A pistol that is run with hot ammunition needs more frequent checks of the recoil spring and the frame. Store ammunition in a cool, dry place. Keep firearms and ammunition locked and out of reach of children and unauthorized users.
Safety and common mistakes
- Never load 10mm Auto into a pistol marked only for .40 S&W. The 10mm case is longer, and the pressure is higher. Some 10mm pistols can fire .40 S&W, but only if the maker says so.
- Do not shoot hot 10mm loads in a pistol that is not rated for them. Read the manual and use the ammunition the maker recommends.
- Treat every firearm as loaded. Keep your finger off the trigger until your sights are on the target.
- Know your target and what is beyond it. A 10mm bullet can pass through a target and travel far.
- Wear eye and ear protection at the range. The blast from hot loads is loud, and indoor ranges amplify it.
- Keep a firm grip. A limp wrist can cause failures to feed or eject with a heavy-recoiling cartridge.
- If you reload, use only published data from a current manual and start low. This page does not contain loading data.
Frequently asked questions
What is the difference between 10mm Auto and .40 S&W?
They use the same .400 inch bullet, but the 10mm case is longer and runs at higher pressure. The 10mm has more power, and the .40 S&W was made to fit a smaller pistol.
Can I shoot .40 S&W in a 10mm pistol?
Some 10mm pistols can fire .40 S&W, but not all, and not always reliably. Check the manual or ask the maker. A .40 S&W pistol must never be loaded with 10mm.
Is 10mm too powerful for self-defense?
It is powerful, and it kicks more than a 9mm. Many people choose a 9mm because it is easier to shoot well and holds more rounds. Practice and training matter more than the cartridge.
Is 10mm good for bear defense?
Many people carry it for that, with hard-cast bullets that penetrate deeply. Bear spray is the first choice for most people. A pistol needs a lot of practice to be useful under stress.
Can I hunt deer with a 10mm?
Yes, with a well-built bullet of 180 grains or more and a careful shot inside about 50 yards. Check local regulations for minimum caliber, energy and barrel length.
How far can a 10mm shoot?
Most practical shooting is inside 50 yards. The bullet travels much farther, so always know your backstop. A carbine in 10mm reaches farther with the same ammunition.
What bullet weight is best for 10mm?
180 grains is a good all-round weight. 200 grains is common for hunting. 200 to 220 grain hard-cast bullets are for deep penetration. Light bullets of 135 to 155 grains are fast but penetrate less.
Can I reload 10mm brass?
Yes. The brass is widely reloaded. Use only published data from a current loading manual and follow its safety instructions.
Sources
Sources reviewed · 29 October 2026