Attached Link: Link to Mk 30 Rifle.

I usually just use the spline modeler and convert any objects I need to into the vertex modeler.  I find the spline modeler to use and faster for most objects.  I tend to desng my models with a lot of subcomponents.  This give more flexibility when skimming.  I actually just completed and uploaded a scifi rifle weapon which took me about an hour in C6 to do.  It is a bit similar to your model so take a look and see what you think.  It was created using only the spline modeler and a few primitives.  Here is the link..

http://www.renderosity.com/mod/gallery/index.php?image_id=1603804