I've got a question about barrel length and avoiding SBR status

[44Dave]

I'm looking at a 14.5" barrel for an AR build.  My flash suppressor is 1.75" long.  If I combine them (solder) do I end up with 16.25" or is some of that 14.5" the threads that disappear into my flash suppressor, effectively making my barrel too short?

Newb

[RobertH]

you can have a 14.5" barrel on your rifle as long as it has a permanently attached flash hider/suppressor and becomes at least 16".  and make sure you attach it correctly and per ATF specs.

[44Dave]

Yes, I was just wondering if the threads at the muzzle were generally counted as part of the measured barrel length or if they were over and above the 14.5" length.  Is there a standard way of measuring, or will different manufacturers do it differently?
I suppose I should call the manu in the morning and just ask.

[justsomeguy]

A barrel is measured from the closed bolt face to the end of the barrel. Use a wooden dowel.

[RobertH]

i don't think the threads are counted until you permanently attach a muzzle device on.  a good way to measure barrel length is this:  put a cleaning rod or dowel down the barrel with your BCG in the upper receiver.  drop the rod down, mark it off and then pull it out and measure it.

but i think someone else should comment to clear up any confusion.


ETA: JSG beat me to it.

[justsomeguy]

Straight from the horses mouth. (So to speak)

http://www.atf.gov/publications/download/p/atf-p-5320-8/atf-p-5320-8-chapter-2.pdf

The ATF procedure for measuring barrel length is to measure from the closed bolt (or breech-face) to
the furthermost end of the barrel or permanently attached muzzle device. Permanent methods of
attachment include full-fusion gas or electric steel-seam welding, high-temperature (1100°F) silver
soldering, or blind pinning with the pin head welded over. Barrels are measured by inserting a dowel rod
into the barrel until the rod stops against the bolt or breech-face. The rod is then marked at the
furthermost end of the barrel or permanently attached muzzle device, withdrawn from the barrel, and
measured.