There is almost assuredly an easier way to manufacture these components but my natural propensity for doing things the hardest way imaginable forced me to utilize the following method.
The goal is to have trunnion mounted capable of elevation rather than traverse turrets to mount the turbo lasers.
First I made the barrel shaped mounts using the method described below. I started with 1/2 inch PVC tubing which for some reason actually has a bore of about 3/4 inch. Now I need a veneer of styrene so I can glue detail to the surface and I need an axle made of styrene to permanently glue the end caps and detail to the axles and I need styrene trunnion receptacles to permanently glue to the upper carapace housing.
All these items must be the same size within a minor fraction of a millimeter i.e. about a hundredths of an inch or the discrepancy will be noticeable.
First I wrapped thins strips of styrene 0.250 inch wide around the center axles wrapping and gluing until the layers made a snug fit in the PVC gun mounts. Making sure the axles were 0.250 inches longer than the mount.
Then I wrapped 0.125 inch strips around the protruding ends of the axles installed in the PVC mounts so when completed there was two styrene discs on either end or the PVC tubes with a 0.5 inch tube running thru the center.
Next I wrapped 0.10 sheet styrene around the PVC to obtain a styrene cover to glue on subsequent detail.
http://i.imgur.com/Pmjal.jpg
This image left to right demonstrate the steps to make the trunnion mounts for attaching the elevation turrets to the carapace and they are build up in much the same manner as the above discription
http://i.imgur.com/tOX52.jpg
Here are the trunnion mounts afixed to the carapace and the inboard reinforcement is glued in place to provide strength when the laser mounts are moved.
http://i.imgur.com/ExJuS.jpg
This side show the rough laser mount in the carapace recess ready to be reinforced.