380 vs 9mm: The Comparison Is Rigged Before Anyone Writes a Word

9mm wins on the numbers: 1.63 times the pressure ceiling and roughly 1.8 times the energy. The honest case for .380 is the pocket pistol itself.

Last updated: September 21, 2026 · Originally published August 29, 2026

9mm is the better cartridge and it is not close on the numbers — 1.63× the pressure ceiling, roughly 1.8× the energy at matched barrel lengths, and defensive loads that reliably do both things a defensive bullet is supposed to do. The honest case for .380 is narrower than it used to be, but it is still real: there are pocket pistols in .380 that have no 9mm equivalent.

What follows is mostly a warning about the numbers themselves. The comparison is measured dishonestly at the source — including by SAAMI and by the ammunition makers — and almost nobody says so.

Quick answers

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The .380 vs 9mm comparison is rigged before anyone writes a word

We downloaded ANSI/SAAMI Z299.3-2022 and read the velocity and pressure tables.

Look at the third row. SAAMI measures .380 in a shorter barrel than 9mm. Every velocity figure that derives from the standard — which is most of them — is comparing across a quarter-inch of barrel before anyone has done anything wrong.

The ammunition makers inherit it. Federal publishes its .380 HST at 935 fps and 192 ft-lb from a 3.75-inch barrel, and its 9mm HST at 1,150 fps and 364 ft-lb from a 4-inch barrel. Those two numbers produce a 1.90× energy ratio, and that ratio is not a like-for-like comparison. It is in the catalog, from the same company, on the same product line.

What happens when you control the barrel

Ballistics By The Inch chronographed both cartridges through a single barrel cut down an inch at a time. At a matched 3 inches:

Computed from those Gold Dot velocities, the energy ratio at a matched 3 inches is about 1.84× — 184 ft-lb against 338. Still a large gap. Just not the one the catalog implies, and arrived at honestly.

The .355 thing

“They both use the same .355-inch bullet” is functionally true and technically false. SAAMI specifies .3565 in for .380 and .3555 in for 9mm. CIP also lists them differently, but by a different amount — 9.04 mm against 9.03 mm. The two standards bodies disagree about the size of the difference, and neither says they are identical. Bore diameter (.348 vs .346) and rifling twist (1:16 left-hand vs 1:10 right-hand) differ as well.

The same 12-inch standard is what the next comparison up the scale turns on too — see 9mm vs .45 ACP, where both cartridges clear it and the argument moves elsewhere.

The FBI question, answered precisely

The standard comes from Urey Patrick’s 1989 FBI Firearms Training Unit paper, and the wording matters:

“a handgun bullet MUST reliably penetrate 12 inches of soft body tissue at a minimum, regardless of whether it expands or not.”

Note reliably. Patrick also wrote that “expansion must never be the basis for bullet selection, but considered a bonus when, and if, it occurs.”

Lucky Gunner Labs shot twenty .380 loads from a Glock 42 — a 3.25-inch barrel — through four-layer heavy clothing into gel, five rounds each. Their verdict:

“None of those 20 loads met the standard of 12 to 18 inches of penetration and at least 150% expansion.”

Three separate things are true here and they get mashed together constantly:

1. On average penetration alone, several .380 loads clear 12 inches. Hornady Critical Defense averaged 13.24 in, Sig V-Crown 12.84 in, Hornady XTP 14.14 in. The flat claim that “no .380 makes 12 inches” is false.
2. On the expansion half of the standard, the two best did not pass even on average. 150% of .355 is .5325 in. Critical Defense averaged .516 (145%); V-Crown .506 (143%). Close, and short.
3. Shot to shot, none of the twenty passed. That is the defensible headline, and it is the one that matches Patrick’s word “reliably.”

The tradeoff is real, and the table shows it cleanly

Sort those twenty loads by expansion and the inverse relationship is unmistakable.

As Lucky Gunner’s Chris Baker put it: “these bullets either expand or penetrate, but they’re not very good at doing both.”

That constraint does not bind at 9mm velocities, and this is the real difference between the cartridges. Federal’s 124 gr HST from a 3.5-inch barrel produced .606 in of expansion and 18.28 in of penetration simultaneously. Speer’s 124 gr Gold Dot: .538 and 18.14. Both criteria, at once, from a compact gun. That is a velocity difference, not a diameter difference.

One useful footnote: Federal’s HST is superb in 9mm and failed to expand on all five shots in .380, running 22.48 inches. Load reputation does not transfer across cartridges.

An important caveat about that dataset

The Lucky Gunner .380 series predates the loads built specifically to solve this problem. Federal’s Hydra-Shok Deep .380 arrived in 2020 and is not in the data. Federal claims 13 to 13½ inches in bare gel and 13¼ to 14 through heavy clothing from 2¾ to 3½ inch barrels, and calls it the first .380 to consistently meet the 12-inch recommendation. Independent confirmation is thin — the one test we found fired three rounds, two of which exited the block entirely, meaning their true penetration is unmeasured.

So: any article using the Lucky Gunner table to conclude “modern .380 fails” is using a dataset that excludes the most relevant modern load. Including, in part, this one. We are telling you that rather than hiding it.

Recoil: the usual explanation is wrong

You will read that .380 recoils more than expected because .380 pistols are blowback. Most modern .380 pistols are locked breech. The blowback examples are a shrinking set — the Walther PPK, the Bersa Thunder, Makarov-pattern guns — not the Glock 42, Ruger LCP, S&W Bodyguard or SIG P365-380.

What actually drives felt recoil in this class is gun weight. Computed free recoil, with the assumptions stated because the charge weights are estimates and nobody publishes the real ones:

The 10.6 oz .380 generates about 34% more free recoil than the 15.7 oz .380 firing the same bullet. A .380 in a comparable-weight gun genuinely is milder. A .380 in a pocket gun is not automatically milder than a heavier 9mm.

We should be straight about the limit here: we found no published instrumented measurement — force plate, accelerometer, or blind panel — comparing felt recoil of .380 pistols to compact 9mm pistols. Everything available is physics, calculation or anecdote. The recoil question has no published empirical answer.

380 vs 9mm on size: the advantage retreated to a niche

SIG’s own two pistols are dimensionally identical — same length, same width, same barrel — because they share a fire control unit and grip module. The entire .380 advantage is 2.1 ounces, and the 9mm holds up to five more rounds. Any 2026 article claiming a general size advantage for .380 is repeating a fact that expired.

But at the true pocket extreme it is still real. The LCP MAX at 10.6 oz and 0.75 inches wide has no 9mm equivalent — the lightest common micro 9mm is 68% heavier and a third wider. The .380’s advantage did not disappear. It retreated from a category to a niche.

For load selection once you have settled on 9mm, see our guide to 9mm self-defense ammunition.

Cost

LuckyGunner, 23 August 2026, cheapest bulk practice ammunition: .380 at 29.0¢ per round against 9mm at 20.0¢. About 45% more, and roughly 55% more comparing brass to brass. Part of that gap is a volume artifact — the cheapest 9mm options are steel-case imports with no .380 equivalent — but the direction is the opposite of what people assume about a smaller cartridge.

What we could not verify

• Hornady’s published test barrel lengths for Critical Defense in either caliber. Their site is JavaScript-gated and three attempts returned nothing. We have not printed Hornady velocity figures for that reason.
• The original publication date of the Lucky Gunner .380 gel series. No date renders on the page.
• Any instrumented felt-recoil comparison between .380 and compact 9mm pistols. None exists that we could find.
• Independent five-shot protocol data for Federal Hydra-Shok Deep .380. Only Federal’s own claim, plus one three-round test with no clothing barrier in which two rounds exceeded the block.
• Defensive JHP pricing for either caliber at a named retailer on a named date — those listings did not render.
• S&W Bodyguard 2.0 dimensions from S&W directly. Ours come from an aggregator; the manufacturer page returned 404.

The practical rule

Carry 9mm if the gun you will actually carry can be chambered in it. The cartridge does both jobs — expands and penetrates — from a short barrel, costs less, and the pistols now come as small as most people are willing to carry.

Carry .380 when the alternative is carrying nothing. That is not a consolation prize; it is the entire legitimate argument, and it is a good one. A sub-12-ounce pocket pistol you have on you beats a 9mm in the safe. If that is your situation, choose a load for penetration first — Patrick’s advice in 1989 and still correct — and accept that expansion is a bonus rather than a plan.

What you should not do is choose .380 for a gun that could just as easily have been 9mm. In the micro-compact class that trade now costs you power, capacity and money, and buys you two ounces.

If the real question behind this one is which pistol you will actually carry, Popular EDC takes it from the carry side rather than the pressure side in its comparison of self-defense handgun calibers from .380 to .45 ACP.

Sources

• Maximum average pressure, test barrel lengths, bullet and bore diameters, twist — ANSI/SAAMI Z299.3-2022, downloaded and read directly
• European figures — CIP TDCC 9mm Browning court and CIP TDCC 9mm Luger
• The penetration standard — Urey W. Patrick, “Handgun Wounding Factors and Effectiveness,” FBI Academy, 1989
• Gel test data and the twenty-load .380 verdict — Lucky Gunner Labs and “.380 ACP: The Biggest Little Caliber”
• Barrel-length-controlled velocity — Ballistics By The Inch, .380 and 9mm Luger
• Catalog velocity and barrel length — Federal HST .380 and Federal HST 9mm
• Hydra-Shok Deep claims — Shooting Illustrated; blowback vs locked breech — The Mag Life
• Pistol specifications — SIG P365-380, Ruger LCP MAX

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James Nicholas

NFA Firearms Manufacturer and Professional Gunsmith. The XDMAN has a talent for taking complex firearms subject matter and breaking it down into an easy-to-understand format that all experience levels can relate to. James is an 07/02 NFA Firearms Manufacturer, a Professional Gunsmith with over 20 years of experience, and a Firearms Writer, Photographer and Firearms Expert. Connect with him on Instagram, X, and Facebook as @therealxdman.

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