N0thing more to add… just use a thin metallic sheet (like the one from a disposable alluminium pan) and make out your barrel…
You can download from flickr (http://www.flickr.com/photos/alessino/7434961380/in/photostream) a complete photo tutorial on how i’m trying to etch some metal parts for my models using the salt water method.
The first part is to transfer the design to etch using the toner transfer technique.
There are a lot of things to learn on how to let this thing work, and for me is still a work in progress.
Some others field tests trying the salt water etching method. I’m start to understand that design of the mask is fundamental, especially about how to connect the piece to the sprue and how much “free space” leave around the object.
Also etching time is primary, while difference between materials (brass or copper) seems to be minimal.
Now i’m working on a more handy etching tank, using a plastic bowl and two stainless steel plates to help distribute better the current inside water.
No big problems on the toner transfer process, using a standard iron the results are very good and the complete transfer process is a matter of 10 minutes from start to etch.