Mike is correct, but this was discussed recently here:

From the PGCA site:
http://www.parkergun.org/forums/forum1/595.html
We who shoot Damascus barrelled guns look for a minimum of .025 wall thickness...measured at 9" from muzzle and breech with .080 at the end of the chambers.

Last edited by revdocdrew; 12/28/06 09:26 PM.