How to Accurately Measure a Gun Barrel's Length

by
posted on September 27, 2026
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gun barrel and ruler

My wife and I are both longtime NRA members. I was looking at a recent issue of one of your publications that featured the SAR9sc Gen 3 on the cover. Once again, I started to question the barrel information. Please note I’m not saying or implying there are any lies or misinformation to deceive us customers; I just want to know for myself the true answers.

Here is my question: If we take a 1911 like my Springfield Ronin and my Kimber Pro Carry II, both in .45 ACP, and measure from where the front edge of the ejection port is to the end of the barrel, I get 3 10/16 inches. If we subtract to account for the rounds I use and add a little for head spacing, I get a net barrel length of 4 1/16 inches. I’m just using a ruler, so I may be off a little, but my question remains the same. When we are teaching someone to enjoy our sport, we use terms like “chamber a round,” so we know that we have a chamber and a barrel. Are we calling it all the barrel, including the chamber and headspace? I hope you can clear this up for me.

Joe Forish, Red Oak, Texas


Thank you both for being loyal NRA members and readers of our publications. Your question is not new and deserves to be addressed, as we in the firearms community strive to increase our numbers. I am glad to learn that you and your wife are doing your part to spread the word and bring more safe and knowledgeable shooters into the fold.

Rather than debating your math and measurements, I think that I can clarify your questions by referring to the recommended methods used by the Sporting Arms and Ammunition Institute (SAAMI) and the ATF. Both use a standard method for measuring barrels in firearms with chambers manufactured as an integral part of the barrel. The procedure is easy to follow.

When performing this procedure, safety is of the highest concern. Remove any and all ammunition from the work area to mitigate the possibility of a mistake. Once the gun is verified clear and empty, close the action as though it were ready to be fired.

Insert a wooden dowel, cleaning rod or other suitable object into the muzzle end of the barrel until it comes to a rest against the breech face where the firing pin protrudes through when firing. Once the dowel is resting firmly against the breech face, mark it at the muzzle with a magic marker or similar marking medium. Next withdraw the dowel and measure the distance between the mark on the dowel and the end that was resting against the breech face.

That measurement is considered the industry standard for pistols, rifles, shotguns or any other type of firearm having a chamber integral with the barrel (Revolvers are treated differently because they have multiple chambers not integral with the barrel).

To measure the barrel length of a revolver, apply all the safety precautions the same as any other firearm. Open the cylinder and place a straight edge at the forcing cone where the bullet transitions from the cylinder to the barrel when being fired. Place a dowel rod or other suitable tool down the muzzle of the barrel until it contacts the straight edge. Mark the dowel rod at the muzzle and withdraw the rod. Measure the distance from the mark on the rod to the end of the rod that rested against the straight edge and that measurement equals the barrel length of the revolver.

To your credit and sharp eye, there are slight variables in advertised barrel lengths and minor changes in some cases to meet government standards that have changed to increase restrictions on everyday citizens’ possession and use in countries outside of the United States.

An example would come from our neighbors to the north in Canada, where that government mandates a barrel length for handguns in civilian hands must be at least 105 millimeters in length. In imperial measurements, that equates to 4.134 inches. A number of U.S. revolver manufacturers simply increased their 4-inch barrel length slightly to comply with that restriction.

This minor change enabled that model of gun to be sold in Canada and the United States without adding another SKU to the product line. For simplicity’s sake and to eliminate confusion, rounding off 4.134 inches to 4 inches for advertising purposes is an acceptable option.

Another example could be seen by converting firearms from their metric manufacturing methods to standard English measurements. The iconic SIG Sauer P220 arrived on the scene in the mid-1970s with an advertised barrel length of 112 mm. This converts to 4.409 inches in English measurement, which for a time was advertised as 4.41 inches in American literature. Later, the number was simplified to 4.4.

Now you know the truth regarding some of the exceptions to the hard absolutes regarding barrel length, so you and your wife can stand on solid ground with this information as you and she educate those new to the firearms community.

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