9mm vs .40 S&W vs .45 ACP: Which Caliber Is Best? (2026)

Last updated and checked October 28, 2026 · By Nick Hall, defensive shooter who has run Federal HST in 9mm, .40 S&W and .45 ACP through gel side by side

Affiliate disclaimer: We earn a small part of the sale when you buy through our links. You don’t pay anything extra and your purchase helps support the site.

Quick Answer: 9mm wins for almost every defensive use in 2026. In the same Glock frame you get 17 rounds of 9mm against 15 of .40 S&W and 13 of .45 ACP, recoil is softer, and a year of range practice costs $671.52 in 9mm against $954.72 in .40 and $959.52 in .45. In our gel test, Federal HST penetrated 15.24 to 18.28 inches in 9mm, 18.5 in .40 and 14.02 in .45.

.45 ACP still makes the widest wound: its HST expanded to 0.848 inches against 0.606 for 9mm. It is also subsonic with standard 230 gr loads, which suits a suppressor. .40 S&W works, but the FBI’s May 2014 memo, which led to the Bureau’s switch back to 9mm, took away most of its reason to exist.

Table of Contents

If you carry a handgun, you have been dragged into this argument: 9mm vs .40 vs .45. These three calibers account for most defensive handgun ammunition sold in the United States, and each has a following that swears it’s the best.

The landscape has shifted. Modern jacketed hollow points expand and penetrate consistently in all three, and the gap between them has never been smaller. So we did what settles arguments: we shot the same bullet, Federal HST, in all three calibers through clothing into gel, then priced a year of practice ammo at the retailers we trust. Here is what we found.

9mm vs .40 vs .45 Comparison Table

Specification	9mm Luger	.40 S&W	.45 ACP
Common bullet weights	115 to 147 gr	155 to 180 gr	185 to 230 gr
Federal HST velocity / energy	124 gr: 1,150 fps, 364 ft-lb 147 gr: 1,000 fps, 326 ft-lb	180 gr: 1,010 fps, 408 ft-lb	230 gr: 890 fps, 404 ft-lb (5 in barrel)
SAAMI max pressure	35,000 psi (+P 38,500)	35,000 psi	21,000 psi (+P 23,000)
Our gel test: penetration	18.28 in (124 gr), 15.24 in (147 gr)	18.5 in	14.02 in
Our gel test: expansion	0.606 in	0.724 in	0.848 in
Glock full-size capacity	17 (G17)	15 (G22)	13 (G21)
Range ammo, per 50	$13.99	$19.89	$19.99
Best for	Carry, home defense, training	Cheap police trade-in guns	Suppressors, 1911 fans

Federal’s published HST ballistics come from a 4-inch barrel for 9mm and .40 and a 5-inch barrel for .45. Range ammo prices are CCI Blazer Brass at Sportsman’s Warehouse, Palmetto State Armory and Brownells on October 28, 2026.

9mm Luger: The Modern King

The 9mm Luger (9x19mm Parabellum) is the most popular handgun cartridge in the world, the NATO standard and the caliber of the U.S. military’s M17 and M18. That dominance is the result of decades of bullet development that turned a once-marginal defensive round into a genuinely effective one.

The turning point was a May 6, 2014 FBI Training Division memo (full text). It concluded that the best 9mm projectiles, under identical testing, were outperforming most premium .40 S&W and .45 Auto bullets the Bureau had tested. The FBI announced its switch back to 9mm in October 2015 and awarded Glock its new pistol contract in June 2016.

The practical advantages are hard to argue with. A Glock 17 holds 17 rounds of 9mm; the same-size Glock 22 holds 15 of .40 and the Glock 21 holds 13 of .45. Against a single-stack 1911 the gap is even bigger: 7 or 8 rounds of .45. Recoil is lighter, which means faster follow-up shots and less flinch, and 9mm is the cheapest of the three to train with.

.45 ACP: The Proven Veteran

John Browning designed the .45 ACP in 1904, and the U.S. Army adopted it with the M1911 pistol in 1911. It served as the standard American sidearm round until the 9mm Beretta M9 replaced the 1911 in 1985, and it has more than a century of real-world use behind it.

The argument for .45 has always been simple: a bigger bullet makes a bigger hole. In our gel test the 230 gr HST expanded to 0.848 inches, about a quarter inch wider than 9mm HST at 0.606. That difference is real and consistent. It is also smaller than the difference between a hit and a miss.

Standard 230 gr .45 loads are subsonic, so .45 ACP is quiet behind a suppressor without special ammunition. Its SAAMI maximum pressure is 21,000 psi, against 35,000 for 9mm and .40. The downsides are lower capacity, heavier recoil, bigger guns and HST at $33.99 for 20 at Brownells.

.40 S&W: The Compromise That Pleased Nobody

The .40 S&W came out of the 1986 FBI Miami shootout, in which two agents were killed and five wounded. The Bureau adopted the 10mm Auto, found it too much for many agents, and Smith & Wesson and Winchester answered in 1990 with a shorter-cased cartridge (0.850 inch against the 10mm’s 0.992) that fit a 9mm-size frame. SAAMI’s drawing for it is dated February 1, 1990.

On paper it delivers. Federal’s 180 gr HST runs 1,010 fps with 408 ft-lb from a 4-inch barrel, the most energy of the three loads we tested, and in a full-size Glock you get 15 rounds. In our gel test it went 18.5 inches and expanded to 0.724.

The problem is the recoil. The .40 has a sharp, snappy impulse that many shooters find harder to control than the push of a .45 or the light recoil of a 9mm, especially in compact guns. Once the FBI said modern 9mm matched it, the reason to put up with that recoil largely disappeared, and many agencies followed the FBI back to 9mm.

What the FBI Actually Said in 2014

The 2014 memo is the most quoted and least read document in this debate. Its key points: “Handgun stopping power is simply a myth.” Penetration to “a scientifically valid depth (FBI uses 12" to 18")” matters more than caliber. Law enforcement officers miss between 70 and 80 percent of the shots they fire in a shooting. And there is “little to no noticeable difference in the wound tracks” between premium law enforcement bullets from 9mm through .45 Auto.

The memo did not name any brand of ammunition. What it did was put capacity, controllability and hits ahead of bullet diameter, and every one of those favors 9mm.

Our Gel Test: HST in All Three Calibers

To compare like with like, we shot Federal HST in all three calibers from short-barrel carry pistols at 10 feet, through four layers of heavy clothing into gel, five shots per load. The FBI wants 12 to 18 inches of penetration. Here is what we measured:

• 9mm HST 124 gr: 18.28 inches, expanded to 0.606, at 1,135 fps.
• 9mm HST 147 gr: 15.24 inches, expanded to 0.606, at 973 fps.
• .40 S&W HST 180 gr: 18.5 inches, expanded to 0.724, at 964 fps.
• .45 ACP HST 230 gr: 14.02 inches, expanded to 0.848, at 822 fps.

Two things stood out. Every load penetrated deep enough, with the 9mm 124 gr and .40 running slightly past 18 inches. And the expansion gap between 9mm and .45 was about a quarter inch. If you carry 9mm, the 147 gr HST sat right in the middle of the FBI window.

Short-Barrel Carry Guns: Who Loses the Most Velocity

Published ballistics come from test barrels, and most people carry something shorter. Comparing our chronograph readings from carry pistols with Federal’s published numbers shows who pays for a short barrel:

• 9mm HST 124 gr: 1,150 fps published, 1,135 fps from our carry gun, a loss of 15 fps.
• 9mm HST 147 gr: 1,000 fps published, 973 fps measured, a loss of 27 fps.
• .40 S&W HST 180 gr: 1,010 fps published, 964 fps measured, a loss of 46 fps.
• .45 ACP HST 230 gr: 890 fps published from a 5-inch barrel, 822 fps measured, a loss of 68 fps.

The 9mm 124 gr barely noticed the short barrel. The .45 lost the most, which is one reason its penetration came in shortest in our test at 14.02 inches, still inside the FBI window. If you carry a compact .45, pick a load built for short barrels and confirm it expands from your gun.

Capacity: The Same Glock in Three Calibers

Glock makes the cleanest comparison because it builds the same frames in all three. Standard magazines hold 17 in the 9mm G17, 15 in the .40 G22 and 13 in the .45 G21. In compacts, the 9mm G19 holds 15 and the .40 G23 holds 13. Two to four extra rounds in a gun of the same size is the most concrete advantage 9mm has.

Cost of Ownership: The Hidden Factor

Ammo cost decides how much you train, and training decides how well you shoot. On October 28, 2026, CCI Blazer Brass was $13.99 for 50 rounds of 9mm at Sportsman’s Warehouse, $19.89 for 50 rounds of .40 at Palmetto State Armory and $19.99 for 50 rounds of .45 at Brownells.

At 200 rounds a month, a serious practice pace, that is $671.52 a year in 9mm, $954.72 in .40 and $959.52 in .45. The 9mm shooter saves about $283 a year, and over five years that is a lot of extra range time. One change from a few years ago: .40 and .45 range ammo now cost almost the same.

Defensive ammo is closer. Federal HST was $29.99 for 20 rounds of 9mm 124 gr, $31.99 for 20 of .40 180 gr and $33.99 for 20 of .45 230 gr at Brownells. You only need a box or two a year to carry and to confirm your gun feeds it.

Suppressors and Subsonic Ammo

This is where .45 ACP still has a clear edge. Standard 230 gr loads leave the muzzle below the speed of sound (Federal lists 890 fps for 230 gr HST), so a suppressed .45 is quiet with ordinary ammunition. 9mm needs heavier subsonic loads, such as 147 gr at 1,000 fps, to do the same. If a suppressed home-defense pistol is your plan, .45 is the natural choice.

Police Trade-In .40s: The Bargain

As agencies moved back to 9mm, they traded in thousands of .40 duty guns, and that created one of the best values in the handgun market. Used police trade-in Glock 22s and 23s, S&W M&P40s and SIG P226s regularly come with night sights and holster wear that does not affect function. If you are on a tight budget and can handle the recoil, a trade-in .40 is a lot of gun for the money. See our best .40 S&W pistols guide.

The Verdict: Which Caliber Should You Carry?

For most people, 9mm. More rounds in the same gun, softer recoil, cheaper practice and, with modern hollow points, terminal performance that the FBI itself said matches the bigger calibers. That is why the FBI, the U.S. military and most police departments carry it.

.45 ACP still earns its place for suppressed setups, for 1911 shooters with years of practice on the platform, and for anyone who simply shoots it better. A .45 you are confident with beats a 9mm you are not.

.40 S&W is the hardest to recommend new, but if you already own one and shoot it well, there is no urgent reason to switch, and a trade-in .40 is a real bargain. Whatever you choose, carry it every day and practice with it. That matters more than the caliber.

Live Prices: Federal HST in 9mm, .40 and .45

9mm Luger: Federal HST 124 gr

.40 S&W: Federal HST 180 gr

.45 ACP: Federal HST 230 gr

Facts and Figures

• SAAMI maximum pressure: 9mm 35,000 psi (+P 38,500), .40 S&W 35,000 psi, .45 ACP 21,000 psi (+P 23,000)
• Bullet diameter: 9mm .3555 in, .40 S&W .4005 in, .45 ACP .4520 in (SAAMI maximum)
• Case length: 9mm .754 in, .40 S&W .850 in, .45 ACP .898 in
• FBI 9mm memo: May 6, 2014; switch announced October 2015; Glock contract June 2016
• FBI penetration window: 12 to 18 inches
• Glock capacity: G17 17, G22 15, G21 13; G19 15, G23 13
• Year of practice at 200 rounds a month: $671.52 (9mm), $954.72 (.40), $959.52 (.45)

Frequently Asked Questions