Barrel Length With Barrel Extension?

GreyEyes

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When a manufacturer lists an AR barrel as 11.5 (Or whatever) inches, how much of that length includes the barrel extension? I think that legally the barrel length is from the muzzle to the face of the bolt on a closed bolt, but I'm not sure how far the bolt actually goes inside of the barrel extension. Does anyone have a barrel lying around they could measure so I might compare a quoted barrel length to actual overall length?
 
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Not really sure what you're asking but the barrel extension doesn't add significant barrel length (per ATF measurement). Technically it contributes to the headspace measurement but that should be no more than like +/- 0.006".

google some photos of the barrel extension and you'll see what I mean
 

GreyEyes

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Sorry, let me rephrase. If I'm looking at let's say a 16" barrel, is the entire assembly including the barrel extension going to measure 16", is it just the portion sticking out of the receiver that is going to be 16", or what?
 
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Sorry, let me rephrase. If I'm looking at let's say a 16" barrel, is the entire assembly including the barrel extension going to measure 16", is it just the portion sticking out of the receiver that is going to be 16", or what?

okay, just google for some diagrams but according to this the barrel would fit in the receiver about 0.62" and then the barrel extension has a lip on it that is probably about 1/8" wide so roughly I'd say the quoted barrel length sticks in the receiver about 1/2".

there are plenty of diagrams like this on the interweb

m16A1barrel.jpg
 

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okay, just google for some diagrams but according to this the barrel would fit in the receiver about 0.62" and then the barrel extension has a lip on it that is probably about 1/8" wide so roughly I'd say the quoted barrel length sticks in the receiver about 1/2".

there are plenty of diagrams like this on the interweb

Good idea, got some good info doing that. Looks like the barrel length is from muzzle to about halfway down the barrel extension, from a quick glance, so I think your rough estimate was pretty spot on. Thanks!

edit:

Arg, maybe I spoke too soon. Seems that some manufacturers measure the whole length, some measure to breech. Diagram of a 20" barrel:

barrellength.png
 
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