we used stainless rod ( I don't remember the alloy, but it's listed in the thread ) but it wasn't that bad... I had my retired buddy make the cases, & the labor is what cost the most... I wish I had the equipment ( & the time ) to do it myself... even though I don't mind giving my fixed income friend some extra $$$ for his fun projects... here is a thread on the build... a couple pics there...
http://thefiringline.com/forums/showthread.php?t=484623