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Barrel Length: How to Measure It and Why It Matters

Barrel Length: How to Measure It and Why It Matters

The gun barrel is an essential element of any firearm. It is the primary pressure-bearing part and the feature which determines the firearm’s chambering and ballistic performance. Every component of a gun barrel must be made of strong materials (typically a steel alloy) and machined precisely to ensure safe operation and accuracy.

Although barrel length matters with every firearm type, the handgun’s barrel length significantly impacts its overall dimensions.

Handguns are often categorized by their size, reflecting the intended use (concealed carrying, duty, competition). The handgun barrel’s length represents a significant percentage of the handgun’s overall length, playing a significant role in determining the handgun’s size category.

What Does Barrel Length Mean?

Most people may refer to the manufacturer’s stated numbers to learn about their particular firearm’s barrel length. However, if your firearm is old or obscure, or if you are a gunsmith or a gun builder, you may need to know exactly how the barrel length is defined and how to measure it correctly.

Measurement methods depend on whether the handgun being measured possesses a barrel with an integral chamber (such as on semi-automatic pistols) or not (as seen on revolvers).

On revolvers, the barrel length is the length between the rear of the forcing cone and the muzzle’s end.

On pistols, it is the length between the back of the chamber and the end of the muzzle.

In both cases, the end of the muzzle includes any permanently attached accessories (such as pinned and welded muzzle brakes, moderators, or compensators).

According to the ATF, there are no restrictions on the barrel length a handgun can possess. However, attaching a stock to a handgun with a barrel length under 16” results in manufacturing a short-barreled rifle (SBR), an item regulated under the National Firearms Act, which is illegal without the proper paperwork.

Barrel Measurement Methods

There are different standards and methods of measuring gun barrels. Only a few conform to government guidelines, such as those outlined by the ATF or by the National Institute of Standards and Technology (NIST).

These guidelines are used by manufacturers and in forensic firearm examination to ensure that measurement methods employed are not only accurate but also readily and independently reproducible.

According to the Scientific Working Group for Firearms and Toolmarks (SWGGUN), proper tools for measuring a firearm’s barrel length include simple devices such as rulers and measuring tapes. However, more precise instruments, such as calipers and measuring rods, are preferred. The ATF procedure recommends measuring from the breech face or closed bolt to the end of the barrel.

Any firearm’s barrel length can be measured using a measuring rod, so long as the starting point is accurate. Before measuring the length of any firearm, remember the basics of gun safety and ensure it is fully unloaded and safe to manipulate.

To measure the length of a pistol barrel or any firearm with an integrated chamber, use a long measuring rod or dowel rod with a smaller diameter than the bore. Insert it inside the bore of your pistol with the slide closed until it touches the breech face.

Use a pencil, marker, or piece of tape on the rod to mark where the muzzle is, remove the rod from the barrel, and use a ruler to measure from the end of the rod to the hash mark you wrote. The measurement you obtain will be accurate and ATF-approved.

On a revolver, you do not need to use a measuring rod. You can use a ruler directly to measure from the end of the barrel to the start of the cylinder, which coincides with the end of the forcing cone.

The Relationship Between Barrel Length and Handgun Size

Most handguns can be grouped in four size categories, which are roughly consistent with their barrel lengths. Remember, these categories are not strict definitions, and that many handguns may straddle the line between two categories.

  • Full-size / Duty: Full-size handguns are generally intended for use by professionals, typically law enforcement or military, where high capacity, accuracy, and controllability are preferred. Full-size handguns feature relatively large frames and barrels ranging in length between 4” and 5” for semi-automatic pistols and between 4” and 6” for revolvers. Full-sizes are typically chambered in potent but controllable calibers, such as 9mm, .38 Special, .40 S&W, .45 ACP, or .357 Magnum.

  • Mid-size / Compact: The term compact generally refers to a size category that is smaller than full-size but isn’t part of the smallest and most concealable pistols possible. This size category is a compromise between the performance of a full-size and the concealability of a subcompact. They feature the largest handguns that can still be practically concealed by most people. Barrel lengths in this category usually range between 3.5” and 4”. Few revolvers meet this definition, making it a class mostly populated by pistols.

  • Pocket / Subcompact / Snub-nose: The general category of pocket pistols encompasses subcompacts (short-barreled pistols) and snub-nosed (short-barreled revolvers). These terms all refer to the same general principle: A short, compact handgun mainly intended for concealed carrying, prioritizing small size over capacity or accuracy. Barrel lengths typically range between 1.875” and 3”.

  • Target / Competition: This category of handguns encompasses guns mainly intended for use at the range, but can also be used as defensive weapons, typically against dangerous animals. This category is where the longest and most powerful handguns can be found. Competition semi-automatics typically possess a barrel length greater than 5”, while target revolvers start at 6”. There is virtually no upper limit of barrel length for handguns of this category. There are handguns with barrels as long as 16”, 18”, and even 20”, typically for hyper-specialized purposes or engineering feats.

Why is the Barrel Length Important?

The barrel length of a handgun is an important consideration to keep in mind for a gun owner, as it affects several factors at once. These include the firearm’s dimensions (in particular, the overall length and weight), sight radius, accuracy, effective range, and most importantly, concealability.

Because the barrel is the most crucial pressure-bearing part of any firearm, it tends to be one of the heaviest parts as well. In turn, the barrel length affects the overall weight and balance of the gun. An excessively long barrel may result in a front-heavy weapon that is more difficult to aim without using a stand or a rest.

On most semi-automatic pistols, the end of the slide sits approximately at or just before the end of the muzzle, meaning that the longer the barrel is, the longer the slide will be. The slide is another pressure-bearing part, typically made of steel, which also influences the gun’s weight.

As any experienced gun owner can tell you, proper sight alignment is the key to shooting any firearm accurately. However, even when you align your sights in what appears to be perfect alignment, there is always a slight amount of uncertainty and deviation; this is called sight deflection.

The longer the barrel, the longer the sight radius: The distance between the rear and front sight. A long sight radius results in less sight deflection, which translates into greater accuracy and effective range.

If you are a concealed carrier or intend to be one, by far one of the most important factors when considering a firearm to carry is the barrel length.

Besides affecting the gun’s overall length and weight, the barrel is the part that sits inside your holster, and in turn, one of the elements of the handgun that must be appropriately concealed.

The longer the barrel, the more difficult it is for you to effectively conceal, as it means more material that must not print or be revealed when carrying.

More barrel length also means more weight. Although a heavier gun absorbs recoil more effectively, it is also less comfortable to carry, increasing the risk of sagging your gun belt or pants down.

Depending on your carrying style, you may not be able to sit down comfortably. For example, appendix carrying may cause the muzzle to dig into your thigh or groin area if your handgun’s barrel is too long.

For all these reasons, most concealed carrying gun owners tend to choose subcompacts and pocket pistols. The overall dimensions of these firearms are small enough for comfortable everyday carry.

Mid-sizes and compacts are the largest size category that can be concealed by most people, but depending on your height, build, and carrying preferences, even pistols of this size class may not be a feasible option for you.

The Takeaway

Choosing the right firearm for your purposes is a balancing act of factors and compromises. Handguns with longer barrels are typically more accurate and controllable, but handguns with shorter barrels are generally more concealable. There is no one-gun-fits-all solution, and you may need to experiment with different handguns until you find the right tool for the job.

Whether you prefer to carry a subcompact, mid-size, or full-size pistol, We The People Holsters offers a large selection of IWB and OWB holsters for all your favorite pistols and revolvers. Our holsters are made out of Kydex, a durable and affordable material that holds up to impacts, abrasion, and moisture, requiring very little maintenance. Best of all, they are 100% US-made.

If you need help or information choosing the right holster for you, contact us at (866) 998-6191. We are happy to answer all of your questions and help you find what you need.