Caliber Comparison — 2026

9mm vs. .40 S&W
— Which Is Better in 2026?

The 9mm vs. .40 S&W debate — history, ballistics, why the FBI abandoned .40, and which caliber holds better private sale value in 2026.

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The .40 S&W Story

Born from Tragedy, Abandoned by the FBI

The .40 S&W cartridge was born directly from tragedy. In April 1986, two FBI agents were killed and five wounded in the Miami Shootout — despite hitting the perpetrators multiple times with .38 Special and 9mm rounds. The FBI concluded they needed more stopping power and developed the 10mm Auto specification. When standard 10mm proved too powerful for many agents, a reduced-power “10mm short” was developed with S&W — the .40 S&W, released in 1990.

The .40 S&W dominated law enforcement from 1990 to the 2010s. Then the FBI abandoned it in 2014. Here’s what happened — and why it matters for your 2026 firearm choices.

The FBI’s 2014 Decision

The FBI’s comprehensive 2014 Ammunition Study found no meaningful terminal performance difference between 9mm +P+, .40 S&W, and .45 ACP with modern quality hollow-point ammunition. The 9mm’s higher capacity, lower recoil, and lower cost made it superior. The FBI returned to 9mm — and most agencies followed.

Head to Head

9mm vs. .40 S&W — The Data

COMPARISON	9MM PARABELLUM	.40 S&W
Bullet Diameter	0.355″	0.400″
Common Bullet Weight	115–147 gr	155–180 gr
Typical Velocity	1,100–1,200 fps	950–1,100 fps
Typical Energy	350–500 ft-lbs	400–520 ft-lbs
Standard Capacity (full-size)	15–17 rounds	12–14 rounds
Felt Recoil	Moderate	Heavy/snappy
Cost Per Round (2026)	$0.22–$0.35	$0.30–$0.48
Terminal Performance (JHP)	Equivalent to .40 S&W	Equivalent to 9mm
Frame Wear	Lower stress on frame	Higher stress — more recoil
Available Pistols	Widest selection	Good selection, declining
LE Current Usage	Dominant and growing	Declining
Private Sale Liquidity	Highest	Good but declining

The .40’s Real AdvantageAt equal velocity, the .40’s larger diameter DOES produce a marginally larger wound channel with FMJ ammo. With quality JHP, modern 9mm expands to .40 diameter anyway — eliminating the advantage. .40 S&W devotees correctly note that bigger bullets are inherently larger, but the practical difference in real defensive use is statistically negligible.

Why .40 S&W Has Value Right Now

The LE Transition Creates Opportunity

Here’s the opportunity that most people miss: hundreds of thousands of .40 S&W Glocks, Sigs, and HKs are flooding the used market as law enforcement agencies transition to 9mm. These are mechanically excellent firearms at below-market prices.

FIREARM	.40 S&W PRIVATE SALE	9MM EQUIVALENT	VALUE GAP	SMART MOVE?
Glock G22 LE Trade-in	$280–$380	G17: $380–$470	$90–$90 cheaper	Yes — identical mechanically
Glock G23 LE Trade-in	$270–$360	G19: $390–$490	$120–$130 cheaper	Yes — plus G17 mag compatible
Sig P229 .40 S&W	$520–$660	P229 9mm: $580–$730	$60–$70 cheaper	Reasonable — same excellent pistol
HK USP .40	$680–$860	USP 9mm: $700–$900	$20–$40 cheaper	Similar — convert to 9mm with barrel

The Conversion OptionMany .40 S&W pistols can be converted to 9mm with a drop-in barrel ($80–$200). A Glock G22 purchased for $320 converted to 9mm with a Storm Lake or Lone Wolf barrel shoots standard G17/G19 ammunition and magazines. Cost-effective path to 9mm.

FAQs

9mm vs. .40 S&W FAQs

Should I still buy a .40 S&W pistol?

Only if the price gap is significant or you already have .40 S&W ammunition stockpiled. For a new purchase, 9mm has wider selection, lower ammo cost, higher capacity, and better resale liquidity. A .40 LE trade-in at $280–$350 can be excellent value — but you’re buying into a declining caliber ecosystem.

Is .40 S&W still a good defensive caliber?

Yes — modern .40 S&W +P hollow-points are excellent defensive loads. The caliber’s decline is about relative economics and capacity compared to modern 9mm, not about terminal performance. If you own a quality .40 S&W and shoot it well, keep shooting it.

Why is .40 S&W harder on the pistol?

The .40 S&W operates at higher chamber pressure than 9mm in a shorter case — creating a sharper pressure spike. Over time, .40 S&W frames show more wear than equivalent 9mm platforms. Glock specifically recommends shorter service intervals for .40 S&W pistols.