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<blockquote data-quote="Super Dave" data-source="post: 1586808" data-attributes="member: 8429">Something about pinning a 9mm AR barrel;The bore is .380&quot;-ish.&nbsp; The od at the threaded end is under .500&quot;.&nbsp; That&#039;s .120&quot; left for the barrel, which is actually less than half (.060&quot;) material, figuring for thread depth, rifling, and that .120&quot; make up two sides. Originally, when I was gonna make my pistol a rifle, I considered making an extra long flash hider, like the Bushmaster Commando, or whatever they call it, but with 1/2-36 threads.&nbsp; I ended up finding one already made for $25.&nbsp; A RRA 10.5&quot; barrel is actually longer.&nbsp; Not sure why the advertise it that way.&nbsp; Measured from the bolt face, with a 5.5&quot; FH, it is just over 16&quot;.&nbsp; The problem is, there is not enough meat there to do a pin/weld job.&nbsp; I called the local BATF, who referred me to a NFA guy at the big office.&nbsp; He explained other methods of attachment, one of which is high temp solder (it&#039;s a specific solder, so look it up if you go that route) on the threads, or a big weld.&nbsp; He explained that if the weapon was to come in to their possession, they put the upper in a barrel, and place a big pipe wrench and twist away.&nbsp; If it comes loose, it wasn&#039;t permanently attached.&nbsp; He said a lot of pinned jobs don&#039;t pass, and agreed on the weakness problem of the end of the 9mms.&nbsp; I ended up welding mine externally to the underside of my barrel with my TIG.&nbsp; It&#039;s a little longer than a 1/4&quot;, and is under a MI SS10 handguard, so you can&#039;t really see it anyway.&nbsp; It is significantly stronger than any small pin, keeping me legal and safe.&nbsp; Just my two cents.&nbsp; Here is the guy I got the FH from;Garrison Mfg. Inc.P.O.Box 231Wauseon, OH 43567419-392-2542If you get one, and want it welded, PM me.&nbsp; I&#039;m happy to do it, and it&#039;s free.</blockquote>

[QUOTE="Super Dave, post: 1586808, member: 8429"] Something about pinning a 9mm AR barrel; The bore is .380"-ish. The od at the threaded end is under .500". That's .120" left for the barrel, which is actually less than half (.060") material, figuring for thread depth, rifling, and that .120" make up two sides. Originally, when I was gonna make my pistol a rifle, I considered making an extra long flash hider, like the Bushmaster Commando, or whatever they call it, but with 1/2-36 threads. I ended up finding one already made for $25. A RRA 10.5" barrel is actually longer. Not sure why the advertise it that way. Measured from the bolt face, with a 5.5" FH, it is just over 16". The problem is, there is not enough meat there to do a pin/weld job. I called the local BATF, who referred me to a NFA guy at the big office. He explained other methods of attachment, one of which is high temp solder (it's a specific solder, so look it up if you go that route) on the threads, or a big weld. He explained that if the weapon was to come in to their possession, they put the upper in a barrel, and place a big pipe wrench and twist away. If it comes loose, it wasn't permanently attached. He said a lot of pinned jobs don't pass, and agreed on the weakness problem of the end of the 9mms. I ended up welding mine externally to the underside of my barrel with my TIG. It's a little longer than a 1/4", and is under a MI SS10 handguard, so you can't really see it anyway. It is significantly stronger than any small pin, keeping me legal and safe. Just my two cents. Here is the guy I got the FH from; Garrison Mfg. Inc. P.O.Box 231 Wauseon, OH 43567 419-392-2542 If you get one, and want it welded, PM me. I'm happy to do it, and it's free. [/QUOTE]

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