Has anyone ever tried (or thought of trying) 6/6 Nylon for there linear shafts? It's got a low coefficient of friction and it seems to be pretty hard and good abrasive resistance. It’s also self-lubricating. Here are a few links about the stuff:

These two links are some specs on it:
http://www.polymerprocessing.com/polymers/PA66.html
http://www.matweb.com/SpecificMateri...&group=General

And here's Enco's page with pricing:
http://www.use-enco.com/HTM/2006/img/644.png

I tried to find some specs on Linear rod (Rockwell hardness, etc) but couldn't really find much as to compare the two materials. But compared to gas pipe it seems like the nylon might win?