Well, I pulled out the vernier caliper which has an electronic readout although it was a somewhat inexpensive one. I read .554 at the right muzzle and between .552 vertically and .556 horizontally in the left muzzle which is apparently slightly out of round.
The thinnest part of the barrels are about half way down the barrels and I calculate .0275" thick which seems pretty good for such a light gun.
I am pretty good at measuring but I may be over my head here without the best equipement nor the most experience at it. Could the measurements be a coincidence between the bore gauge and the vernier caliper? I think I should bring the barrels next time I am at Dewey Vicknair's place or at the next show where that guy sells that caliper that goes 7 inches or so into the bore and have him measure it. Here in my amateur shop it looks like cylinder/cylinder to me.
