OK, time for the Barrel Grinch to chime in. Once you finish this barrel, do proof test it with two overloads. Whatever any of us may say about proof testing a steel barrel, it is imperative to proof a forge-welded barrel to determine if the weld is strong. With forge welds there is such a thing as a "dry weld", a joint that looks welded, even under a modern microscope (same is true of electric resistance welds). However under stress it will come apart nicely.
A power hammer would be a very good thing to have. Hand-forged barrels tend to fail proof at a higher rate.
The following is taken from Chapter 5 of Harpers Ferry Armory and the New Technology, by Merritt Roe Smith. It has the best description anywhere, of gun barrel manufacture. Get thee a copy, perhaps from abebooks. Read Chapters 4 & 5. Then re-read them again, for a few days.
At Harpers Ferry Armory the loss in proof of hand forged barrels was typically 25% and during the 1830's could exceed 40% . At Springfield Armory where they used trip hammers the loss in proof was typically 10%.
In other posts I have mentioned the importance of a magnetic particle inspection for rifle barrels. In my own opinion this is inappropriate for a forge welded barrel. First, regardless of anyone's opinion, there is simply no body of industrial experience, published at least, on mag particle inspection of forge welds, especially in wrought iron. I believe iron was last puddled in this country about 1961. For this reason I would suggest you consider an old-fashioned proof test to determine if that forge-welded damascus barrel were sound.
Having no personal experience in the matter I really can't say more than "what I read in the papers". Which is, from Col. Bomford to the Secretary of War, John Calhoun, August, 1823:
MUSKETS
Proof and inspection of Barrels
The inspector will first examine the barrel . . . free from ring bores, cinder holes, flaws, cracks, and other defects . . . All the barrels which may pass this examination, will be closed at the breech, either with proving plugs or breech pins, and proved as follows, viz.
1st charge - One eighteenth part of a pound of powder; one lead bullet, weighing one-fifteenth part of a pound; and two paper wads, each to measure three fourths of an inch in length, after being well rammed; one of the wads to be placed on the top of the powder, the other on the top of the bullet. The whole to be well rammed with copper rods.
2nd charge. - One twenty-second part of a pound of powder, with one bullet, and two wads, as in the first charge.
. . .
The barrels which resist the proof, will be cleaned and examined, and, if no defects are discovered, the vents will be stopped, and the bores will be filled with water. If proving plugs have been used, they will be removed, and the breech pins will be screwed in before the water is applied. The barrels, when filled with water will be left standing about six hours, when they will be again examined; and if no water has passed through the breech, or made its appearance on the exterior of the barrel, nor any other defects observed, they will be received. The marks of reception will be as follows, viz: the letters U. S. to be placed on the top of the barrel, one inch distant from the breech, the initial letters of the inspector's name, with the letter P. under them, to be placed to the left of the letters U. S.; which marks will be made by the inspector.
This is part of a report from J. C. Calhoun to President Monroe. That is how they dealt with forge-welded wrought iron .69 caliber smoothbore musket barrels. One eighteenth part of a pound is 390 grain, one twenty-second part of a pound 320 grains, or calculate it yourself.
