I have a buddy who is a CNC Machinist and has offered to help me construct a Service Rifle Float tube. I can purchase a standard barrel nut for about $5.  He has scrap tubing of about any gauge I would want.  All I need is a drawing, or a description of how to make one of these things.  I have read that the better float tubes are three-piece assemblies that allow for the proper indexing of the sling swivel.  All of the float tubes that I have seen pictures of are completely assembled so I don't really understand how it all goes together and what the different pieces look like.  Besides being hopelessly cheap, the other reason I want to make this myself is because I am thinking of making the float tube out of aluminum instead of steel, to keep the weight down.  Can anybody offer some info or pictures?  Thanks.