You may have noted from time to time I warn against the use of welded seam barrel liners.
The issue isn'’t the strength welded tubing. Welded seamed tubing can be very strong. Your brand new cannon isn'’t going to burst on first firing because it has a welded seam liner.
It's the very nature of welds themselves that create the problem. Welding often leaves inclusions and micro-pores in the metal. These inclusions and micro pores can collect moisture and fouling.
When fired, particles of blackpowder fouling can be blasted into the micro-pores. The expansion of the metal from pressure and heat can allow these microscopic particles to be driven deep into the metal. When a wet swab is passed down the bore the steam can further imbed this fouling as well as cause condensation with in the incclusions. Over a period of time this fouling starts the corrosion process. The corrosion process takes place in the metal. The corrosion slowly grows until it is too weak to retain the pressures applied to it. It can result in anything from pin hole leak to a catastrophic rupture.
Under normal use it's a problem that might not manifest itself for years.
That’s what happened with many Damascus Shotgun barrels. These guns were used for years before any problems occurred. I have seen several of these burst damascus barrels and there did not appear to be any visible corrosion on the inside or outside of the barrel. One characteristic I did note, on a couple of the barrels was a darkening of the pattern of the seam in the area where an inclusion was corroding.
I can recall the first black powder cannon I built. It was made from Schedule 80 welded tubing. When the rust started to bubble the paint over the seam we tossed that tube out and built another. We never had an accident. I don’t know why. We were darn lucky.
Twenty years ago when I started serious shooting and building of model muzzleloading artillery one of the first warnings I received was about the use of welded seam tubing. Don’t Use it, I was told!
Back then the magazine “The Muzzleloading Artilleryman” often had articles on cannon firing accidents. Poor casting techniques, lack of liners in cast guns and welded seam tubing failures were prominent. Even back then organizations like the North South Skirmish Association knew about the weakness in welded seam liners and had rules against their use.
So, you didn’t know about the problem with using welded seam tubing for making a cannon barrel and to save money you bought a cannon with a welded steel liner. Should you get the cutting torch out and make scarp metal or maybe stand it on end and use it as an umbrella holder.
NO!
First you are going to have to deal with the ridge of weld going down the seam.
Inspect it. Make one of those inspection mirrors described in the More Complete Cannoneer. Look the seam over. Do you see any defects? Mark the muzzle of your gun right over the seam so you know where the seam is in your tube.
Ream the barrel. After reaming inspect the tube for defects. That’s why you made the mark so you know where the seam is.
Next hone or polish the bore. Inspect the bore again looking for defects.
What do you do if you do find a defect? If it’s a brand new unfired gun, I would contact the manufacturer.
You could also remove the liner and install a new liner.
If you don’t find a defect, shoot your gun! Watch for signs of gas leakage between the liner and outer casting.
When you clean the gun, watch for water seepage from between the liner and casting. Make sure you use plenty of hot water to clean you bore.
After every shooting inspect the bore with your inspection mirror. Make sure your bore is clean and dry before you oil it and store the gun.
Several days after firing inspect you bore again, look for signs of discoloration and seepage along the seam. Wipe the discoloration with a dry white cloth and check the color. If you suspect a problem check it very thoroughly and if there is any doubt take the gun out of service until it is repaired.
If you are buying a gun with a lined bore ask if the liner is seamed or seamless. If it is seamed and the gun is used have it inspected by someone knowledgeable in the construction of cannons before buying. Better yet have it X-rayed for defects.
If you are buying a new cannon insist on a seamless liner. Do not let anyone talk you out of it.
