9mm, 380 ACP, 40 S&W or 45 ACP for Concealed Carry?

Posted by Recoil Gunworks on Feb 13th 2026

9mm vs .380 ACP vs .40 S&W vs .45 ACP: Which Is Most Effective for Concealed Carry?

Choosing a carry caliber is one of the most debated topics in the defensive shooting community. The truth is, modern ammunition has significantly narrowed the performance gap between popular handgun calibers. Today, effectiveness is driven less by diameter alone and more by penetration, expansion, controllability, and shot placement.

Let’s break down four of the most common carry calibers: 9mm, .380 ACP, .40 S&W, and .45 ACP.

9mm: The Modern Standard

The 9mm has become the dominant defensive handgun caliber in both civilian and law enforcement circles.

Advantages

  • Higher magazine capacity

  • Manageable recoil

  • Broad ammunition selection

  • Strong performance with modern hollow points

Modern 9mm defensive loads such as Federal HST and Speer Gold Dot routinely meet FBI penetration standards while offering consistent expansion. Advances in bullet design have largely eliminated the historical performance concerns associated with 9mm.

For most carriers, 9mm offers the best balance of capacity, recoil control, and terminal performance.

.380 ACP: Compact and Concealable

The .380 ACP is popular in ultra-compact pistols designed for deep concealment.

Advantages

  • Smaller firearm platforms

  • Reduced recoil (in some models)

  • Easy concealability

Considerations

Because .380 operates at lower velocity, bullet selection becomes critical. Not all hollow points will meet recommended penetration standards from short barrels. Some shooters opt for carefully selected defensive loads that maximize penetration while still offering some expansion.

.380 is often chosen when concealability outweighs other considerations.

.40 S&W: The Compromise Caliber

The .40 S&W was developed to bridge the gap between 9mm capacity and .45 ACP bullet diameter.

Advantages

  • Heavier bullet than 9mm

  • Generally good penetration

  • Strong law enforcement history

Considerations

Recoil is typically sharper than 9mm, which can slow follow-up shots for some shooters. In recent years, many agencies have transitioned back to 9mm due to advancements in bullet technology and improved shootability.

Still, .40 S&W remains a capable defensive round when paired with quality ammunition.

.45 ACP: Large Diameter, Proven History

The .45 ACP has a long-standing reputation for effectiveness.

Advantages

  • Larger bullet diameter

  • Typically heavier projectile weights

  • Moderate operating pressures

Considerations

Lower magazine capacity and larger firearm size can be trade-offs. Recoil tends to be more of a push than the snap of .40 S&W, but it’s still greater than 9mm for many shooters.

With modern hollow points, .45 ACP offers consistent expansion and adequate penetration, but the ballistic gap between it and 9mm is smaller than ever.

Penetration and Expansion Matter More Than Diameter

Across all four calibers, effective defensive performance depends on:

  • Adequate penetration (commonly cited 12–18 inches in ballistic gel)

  • Reliable expansion

  • Consistent firearm function

  • Shooter accuracy and recoil control

The difference in permanent wound cavity between modern 9mm, .40 S&W, and .45 ACP hollow points is often measured in fractions of an inch. Shot placement and the ability to deliver fast, accurate follow-up shots frequently outweigh caliber differences.

Recoil and Capacity Considerations

When evaluating carry effectiveness, consider:

  • Can you control recoil under stress?

  • Can you make fast follow-up shots?

  • Does your chosen platform offer sufficient capacity?

  • Can you carry it comfortably every day?

A caliber you can shoot well and carry consistently is more effective than a larger caliber you struggle to manage.

The Bottom Line

Each of these calibers — 9mm, .380 ACP, .40 S&W, and .45 ACP — has proven capable of defensive use when paired with high-quality ammunition and proper shot placement.

The practical differences in modern defensive loads are far smaller than internet debates often suggest. With high quality defense ammo, a bullet from any of these in center mass should be effective.

Choose the caliber you shoot best, verify reliability in your firearm, and train consistently. Skill and preparation matter more than caliber alone.

SHOP ALL DEFENSE AMMO