i agree about the pvc and shipped a good bit of ebay stuff that way but i did have one problem with a package that was "lost" for a while. it finally showed up but the PO said they have lots of trouble with round packages simply because they roll and are a lot easier to get misplaced on trucks because they don't stay put very well and end up going elsewhere than intended for a while.
a buddy of mine found a plastic case for holding arrows somewhere that did come in a good cardboard box. i think he said it was $20. it didn't have any foam but all sorts of foam is easy to get. guns have to be taken apart to fit in it but it held a heavy barrel FAL. we used it back and forth for quite a while till one particularl dealer threw the box away.
i also had a really good shipping box i kept for that purpose and sent a perazzi to collectors firearms. when it was sent back they'd thrown my box away and sent it back in what amounted to a piece of cardboard sheet wrapped around some styrofoam ends. pure piece of crap packaging. i can't back up what everybody else is saying on the thread about them regarding how well they pack guns because that was certainly not my experience.
