Here's 2 of suppliers of hypodermic tubing that our club members use.
http://www.smallparts.com/s?searchSize=15&field_material_browse=16414661&searchBinNameList=subjectbin%2Cmaterial_browse%2Citem_shape%2Cmeasurement_system%2Cbrandtextbin%2Cenc-merchantbin%2Cavailability_class&refinementHistory=subjectbin%2Cmaterial_browse%2Citem_shape%2Cmeasurement_system%2Cbrandtextbin%2Cenc-merchantbin%2Cavailability_class&searchKeywords=hypodermic%20tubing&searchNodeID=16414261&searchRank=price
http://www.componentsupplycompany.com/
I also have a chart that gives the scale size tubing to use for various guns in various scales. Sorry though, there is no list for 1/700 scale, only 1/72, 1/48, 1/35, 1/32, 1/24. It has sizes for .30 and .50cal., 20, 25, and 30mm and some British and Russian Calibers. If anyone wants one, send me a PM and I'll try to get one to you. I can't seem to post pics on the Forum but I can e-mail it to you.
Hope that all this helps you.
Jim
Main WIP:
On the Bench: 1/48 Tamiya - Vought F4U-1A Corsair for Group Build 'Absent Friends' 50% 1/48 Encore Models - A-37B/OA-37B Dragonfly 50%
I keep hitting "escape", but I'm still here.