Ain't there someone out here that can take 10 minutes and measure their carbine barrel??? A member has offered to turn a piece of round bar stock for me to make a DUMMY 10.5 barrel.. But any lightweight carbine barrel dimension will work..I have a barrel extension,so what I need would be basic contours out to the section in front of the sight base.Start with the back end  of the barrel extension,measure to the shoulder that the handguard cap sits against,then out past the FSB.. I'll need the diameters as well. Please help,,this project will be use for a living history display memorial day weekend at Pres FD Roosevelts mansion/library to honor our Vietnam vets....

I can measure my Colt 9mm lightweight barrel, the external profile should be pretty close as long as I correct for the difference in barrel length between 9mm and 5.56 barrels.

Do you want a dummy 10.5 or 11.5?  The 11.5s were more common I thought, and later production.  For the 10.5 you would also probably need a no-bayonet lug FSB which might be hard to find.

Hi Bro,,I'm lookin to do an XM177 or early GAU5 type lookalike with the early 10.5 barrel.I have an old slickside upper that I will be using...Any info you can send my way would be greatly appreciated!! thanks.Rob.

Guess I missed your thread, Rob. Anyway, barrel diameters for my superlight barrel are as follows: barrel extension is .750" and tapers to .565" under the handguards, then up to .675" behind the FSB. Drops off to .625" for the FSB, then goes to .510" in front of the FSB to the muzzle. The FSB is right at 2" front to back, then we got right at 8" from the handguard cap to end of the barrel extension. Hopefully somebody with some calipers can give you exact dimensions on the lengths.

Ok here are the measurements I got from my barrels:

No CAD program so I just MSpaint/Photoshopped up something that hopefully gets the information across.



The rear of the "ring" where it butts up against the receiver is the reference point for the length measurements.

I looked through the Retro "real deal" photo thread and the shorter XM117 types were more common than I thought.