What Barrel Length Is Best for .40 S&W?
Woody's answers are based on published federal and state law. Not legal advice. Consult a licensed attorney for your specific situation.
The optimal barrel length for .40 S&W is 4-5 inches. This range maximizes powder burn efficiency while maintaining practical handling characteristics for most applications.
How This Affects Your Shooting
The .40 S&W was designed around a specific powder charge that reaches optimal performance in moderate barrel lengths. Unlike magnum cartridges that benefit from longer barrels, the .40's powder capacity and burn rate characteristics plateau relatively early. Understanding this relationship helps you choose the right barrel length for your intended use without sacrificing performance or adding unnecessary weight.
The Detail
The .40 S&W cartridge achieves nearly complete powder burn within the first 4 inches of barrel length. The cartridge uses relatively fast-burning powders in moderate charges, which means most of the pressure curve is exhausted before the bullet travels far down the bore. You'll see minimal velocity gains beyond 5 inches, typically less than 25-50 fps per additional inch.
Barrels in the 3.5 to 4.5 inch range represent the sweet spot for most .40 S&W applications. This length allows the powder to burn completely while keeping the overall package manageable. Shorter barrels around 3 inches will sacrifice some velocity and may produce more muzzle flash, but the performance loss is relatively modest compared to what you'd see with rifle cartridges.
Longer barrels beyond 5 inches don't provide meaningful ballistic advantages for the .40 S&W. The diminishing returns kick in quickly, and you're mainly adding weight and length without proportional performance gains. Some competition shooters prefer longer barrels for sight radius benefits rather than velocity improvements.
The cartridge's pressure characteristics also favor moderate barrel lengths. The .40 S&W operates at relatively high pressures, and the optimal barrel length allows this pressure to work efficiently without the bullet spending excessive time in the bore after pressure has dropped significantly.
Build Impact
For a practical build, stick with 4 to 4.5 inches unless you have specific requirements pushing you shorter or longer. You'll get excellent performance without unnecessary bulk, and most holster options will accommodate this length range well.