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Posted: 7/10/2007 9:05:37 AM EDT
| Does anyone know the standard length of the FS threads (the length of the barrel that's stepped down and threaded)? Thanks alot. |
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It also depends on whether the barrel maker takes the thread all the way to the larger bbl diameter, or leaves a shoulder at the base of the thread. Also of note is that the shoulder can either be the O.D. of the thread or the I.D> of the thread grooves...I've seen them both ways over the years. Steve/RRA |
I personally reduce the area against the barrel to the ID of the threads like this:  This ensures that no muzzle device will "run out of threads" before it hits the shoulder. Most muzzle devices get installed with a crush washer and having the area against the shoulder made to the OD is better for use with crush washers. On NON-NFA XM177 builds, I do a special threading with a shoulder to center the grenade ring: 
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