Cat,
The barrel is brass shafting, scrap, probably 360 but I don't actually know. I redrew one of the barrels off the CD that the navy sells of the constitution, and scaled it down. The taper was roughed out in steps then filed smooth in the lathe. The mouldings were cut freehand using a bit with a round, 1/64, radiused end. A bar is put in the lathe's tool holder and positioned close to the work then the cutting bit is rested on the bar, held in the hand, and the brass is cut freehand as you would do in a wood lathe with a gouge. The "Breech" was done the same way including the cascabel. As long as the rest stays close to the work, 1/8 to 1/32, it seems very safe.
The muzzle:
Moulding detail and breech:
The tool I used"
I milled two slots in the back of the barrel and silversoldered the hinge parts, then milled a slot in the breech and silversoldered the center hinge in. There will be a stop bolted to the rear axel that the hinge will close against when the barrel is down, then once it is fired it the barrel will tip up and the breech will open to reload.
Detail of the moulding: