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Posted: 7/9/2007 6:23:16 PM EDT
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When people measure their barrel, does it start from the barrel extension to the end of the flash hider? Trying to check if some 14.5" are 16" with the A2 flash hider. I am measuring from the barrel extension (behind the front lug where the bolt carrier ends) to the end of the flash hider. I've seen people measure from the receiver to the end of the flash hider but I think the barrel extension should count since it's part of the barrel. That would mean the measurement would actually be a half inch from the end of the receiver. What do you all think? |
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If you are talking M4 style barrels, the difference is easy to spot. A 14.5" M4 barrel will have less barrel length foward of FSB A 16" M4 barrel will have more barrel length forward of the FSB. They both share the same gas system length. Therefore the FSB's are pinned in the same location on 14.5" and 16" M4 barrels. Both measurements are determined at the end of the threads on the muzzle. HS1 |
+ 1 This is the correct answer. |
thanks. that's what i was looking for. i guess the only exception to this is a non-permanently affixed flash hider/muzzle break will not count towards the 16". |
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It's unlikely that a 14.5" barrel with a an A2 permanetly attached would measure 16" from the breech face to the end of the permanent A2. In fact, that's why CMMG makes a 14.7" barrel with an A2 permanently attached - to be sure to legally exceed the 16" requirement, and it looks VERY similar to a 14.5" |
yeah i had noticed that, it's a tad short. glad i haven't mounted it on anything and i own a pistol lower  so let this be a warning to those with 14.5" barrels with a1/a2 flash hiders, you probably aren't compliant. it gives you an excuse to upgrade to that phantom or vortex you've been eyeing though  you might be able to get away with using 2 crush washers but that would be a little ugly imho. get the vortex and call it a day. |
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"Trying to check if some 14.5" are 16" with the A2 flash hider. I am measuring from the barrel extension (behind the front lug where the bolt carrier ends) to the end of the flash hider." Another way: assuming the FH is permanently pinned, grab a retractable tape measure, hang the metal tap over the end of the BBL EXT and notice the measurement at the end of the FH. THEN, subtract 3/8", since this is the distance that the bolt face intrudes into the BBl EXT. If the FH is not permanent pinned, remove it and follow same process above, measuring to end of barrel. |
No. Close the bolt, and make sure the firing pin is back. Drop a rod down the barrel. Mark the rod at the end of the barrel (with any removable muzzle devices removed). Measure the rod from the end to the mark. That is how the BATF measures barrels. |
Thanks for the graphic. Basically you can measure the barrel to the receiver and then add .75". I assume if it's a phantom, you measure from the end of the prongs right? If that's the case, does the longest side of a slant brake like an ak47 break count towards the 16" (not that i'm mounting one, just for discussion)? 
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It's easier to measure to the end of the barrel extension and subtract 3/8" from the total length of the barrel. Even with the barrel installed on a receiver, it's easy top see that the barrel extension ends at the inside front wall of the upper receiver so you can snap a tape measure to that edge and subtract 3/8" from the overall length. The end of the phantom is the measuring point as would the the end of that slant brake. |
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