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1/22/2020 12:12:56 PM
Posted: 1/20/2015 10:36:08 PM EST
What is the current ATF approved method of pinning and welding a muzzle device on a 14.5" barrel?
Link Posted: 1/20/2015 11:10:15 PM EST
This should help explain it.

http://blog.del-ton.com/2013/03/sbr-basics-of-short-barreled-ar-15.html

Scroll down to the bottom of the page for the info you're wanting.
Link Posted: 1/21/2015 1:10:16 AM EST
[Last Edit: 1/21/2015 1:11:35 AM EST by AR-4C]
Below is from Chapter 2 of the BATFE's NFA (National Firearms Act) Handbook. The best method in my opinion to limit the HAZ or heat affected zone when permanently attaching the muzzle device is to blind-pin the muzzle device. Which is also the method I used using a TIG Welder to bring my 14.625" barrel to 16.875" two years ago.


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 The rod is then marked at the furthermost end of the barrel or permanently attached muzzle device, withdrawn from the barrel, and measured.
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