How to Properly Measure Barrel Length

Larry Potterfield • January 18, 2023

Barrel length is important, and it might be very important. Let me tell you why and show you how to measure it.

The National Firearms Act was enacted in 1934. One of the requirements of this act was the registration and taxing of firearms that had short barrels. Today all rifles must have barrels longer than 16 inches and all shotgun barrels must be longer than 18 inches to avoid federally required registration and taxes.

It's a straightforward process to measure barrel length. All that's needed is a cleaning rod or dowel rod, some masking tape and a yardstick. A single barrel break open shotgun, like this Remington Model 1893 side lever, is the easiest to measure. Putting a yardstick along the outside of this barrel measures 30 inches. However, the official procedure is to measure from the breech face to the muzzle end of the barrel. To do this I slide a dowel rod down the bore until it touches the breech face. This barrel officially measures 30 inches.

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A side-by-side shotgun is measured the same way. With the yardstick, the barrels of this L.C. Smith 410 bore measure 26 inches. Sliding the dowel rod down the bore, until it contacts the face of the breech, verifies the measurement.

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Pump and semi-auto shotguns are a bit more of a challenge. On this Remington Model 11, some people might be confused as to exactly where the barrel begins. It's not how much barrel is sticking out of the receiver, but the distance from the muzzle end of the barrel to the face of the bolt when closed. This barrel is 28 inches long.

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With the barrel removed it's easy to see that there could be three ways to measure the barrel length. However, only one is correct.

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This pump-action Remington 870 barrel is measured exactly the same way. The dowel rod is slid down the barrel until it makes contact with the closed breech face; this barrel is 26 inches long.

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If a barrel has a permanently attached choke, or other muzzle device, it's included in the barrel length. This choke tube is removable, and therefore is not included in the barrel length. So, this barrel measures a bit over 26 inches.

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Rifle barrels are measured using the same technique. In the case of this Stevens Crackshot, a cleaning rod is inserted into the muzzle end of the barrel until it makes contact with the closed breech block. A piece of tape is used to mark the end of the barrel. The rod is withdrawn and measured; this barrel is 22 inches long.

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The process is exactly the same, whether it's a bolt action like this custom Remington 700 safari rifle or a semi-auto like this Winchester Model 7.

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A revolver barrel is measured from the muzzle to the face of the cylinder. In the case of this Smith & Wesson Pre-War Registered Magnum, it's eight and three-quarters of an inch.

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A semi-auto pistol is measured from the muzzle to the breech-face. This Colt 1911 barrel is five inches long.

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It's important to measure barrel length, and now you know why and the official way to do it.

--Larry Potterfield