Wayne York will go down to .200 over bore diameter. He says there's little pressure at the muzzle.
I am sure he is right, I measured a dozen or so factory factory barrels of the featherweight or lightweight class...my arbitrary .144 ish wall thickness is not based on engineering fact...just what the mfrs were doing. Pressure of course is not the issue, if there is a front sight to be fitted, it's nice to have some meat to work with....unless you sweat solder or use a sweat band.
