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put a rod down the barrel with chamber closed, mark where the fs (if perm attach) ends, measure  

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This sounds like an idiot-proof way of measuring. Can they really use a method that is so simple?

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The ATF doesn't use a tape measure. They drop a wooden dowel down the barrel on a closed bolt. The measurement of barrel length is from closed bolt to end of permanently attached muzzle device. A tape measure may give a false reading because of the barrel extension (into which the bolt closes)

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The dowel is longer than the barrel. They drop it down the bore so it stops on the closed bolt and mark it at the muzzle end, then measure the length from the bolt end of dowel to the muzzle mark.

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The dowel is longer than the barrel. They drop it down the bore so it stops on the closed bolt. It is longer than the barrel so it protrudes from the muzzle end. They then mark the dowel at the muzzle end. They then measure the length of the dowel from the bolt end of dowel to the muzzle end mark that they made on the dowel.  It is a very simple process. The law says barrel length is measured from a closed bolt.

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I don't assume sarcasm, because uninformed is so familiar to me. Sarcasm has no place in this thread. Clarity, in how this is done, and why it is done that way, is critical. It is a mistake that can ruin your life and the visual aid for the jury is a dowel. It is hard to defend, so one can't afford to f@#k it up. I saw it done wrong on a shotgun last week and had them immediately weld an extension to bring it into compliance. This particularly, is not an academic issue.





Since we became members, this has been research and posted several times with varying references to authorities..  In the archives somewhere, you'll find an ATF letter. Of course, they use a tape meausure or ruler to measure the dowel. They do not use a tape measure to measure the barrel directly. It is an important distinction, because you cant measure the barrel accurately for this purpose by using only a tape measure. I just know that it is a VERY important thing to fully understand BEFORE you cut.

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Gathering the parts for a 14.5 mid-length upper. Trying to determine overall barrel length with my chosen muzzle device before i send it off to be pinned. My question is...If Mr. (or Mrs.) ATF comes to measure my barrel, where do they hold the end of the tape measure at the receiver end? My 14.5" barrel is only 14" to the barrel nut flange, 15" to the end of the extension.

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.....they should have a.... rod......with a sliding register.....Hold the rod against the.....face.....slide the register down until it stops.......pull it out and.......I'd be surprised if they did not have........an infraction.