Drew, thank you for that link!
I did some measuring, and believe these to be fairly heavily constructed. The 30-inch tubes weigh 4 1/2 pounds. They taper from 1.050 inches at the breech plug joint to .825 at the muzzle.
Have them soaking, nipples down, in penetrant. Hope to "draw the cones" soon.
I have got to get one of those cheap Chinese LED endoscopes and a have a good look inside.