Here is the one I just took off of my 42 1 1/2 ton. http://s1293.photobucket.com/user/Milibolt/media/Big%20Truck%20G%20506/DSCN7827_zps0aa1a95c.jpg.html
As you can see there is a screw inside the barrel. Yours may very well be different but thought I would throw it out there.

Good luck on gettin yours apart without busting it.

Tony


1942 Chevrolet 1 1/2-ton (G-506 Military) Panel
In the Stovebolt Gallery
Short video
Longer video