In recent years a number of people entering the cannon hobby have focused on steel as a material for construction of replica cannon. Because of the higher strength characteristics of steel the assumption has often been made that an "all steel" cannon would be "safer" than one made from the traditional materials, cast bronze or cast iron (properly sleeved).
We have cautioned many phone callers that fabricated steel cannon are not inherently superior to cast iron or bronze products; it all depends on how well they are made. Once painted, steel cannon replicas can all look alike.
An example of what can be concealed in a fabricated steel gun tube is revealed in the photos which accompany this article. The gun is a full-size replica 3-Inch Parrott, smoothbored only.
The owner bought it used and it is said to have been produced by a widely advertised maker who touted the fact that the tube is all steel, having been deep hole drilled from bar stock. We understand that the maker of this cannon can no longer be found in the U.S., although some are looking for him, for financial reasons.
A gas leak at the breech band was the first problem noticed. Stopping the vent during loading would not prevent air movement in and out of the tube with this condition. This leak was dramatically illustrated by plugging the vent with a wood dowel and fitting a muzzle tampon, with water hose fitting.
Our first presumption was that the tube could possibly be rendered usable by installing a proper vent piece.
A closer inspection of the cascabel area revealed a fine circular crack at the root of the knob, which possibly implied that some failure at the breech may be about to happen. This possibility encouraged the owner to make a very detailed survey of the gun, finally to the point that he ordered it to be cut apart for study.
Cutting the breech in half revealed that no breech failure was likely since the bore was indeed drilled into solid bar stock. But many other potentially dangerous conditions had been introduced in the manufacturing process.
Most frightening was the knob. It was turned from a separate smaller diameter bar and installed in a tapered counterbore in the cascabel, by welding. The weld was very thin, probably most of it had been removed in the finishing process, leaving virtually nothing to hold the knob.
After the saw cut parted the knob, one half of it fell out without any prompting. Several persons who had handled the tube by lifting on the knob were outraged at the needless risk they had just undertaken. A 900 pound falling gun tube could be just a fatal as any gun tube which might burst!
Attachment of a separate knob can indeed be done, but must involve close tolerances, accurate work and a well-designed threaded stem of large diameter. The process viewed in this specimen was totally dangerous.
The chamber shows there was no attempt to radius the bottom of the bore. Sharp corners tend to hold wet carbon buildup and promote premature ignition.
No attempt was made to shrink the breech reinforce onto the main tube. The generous gap between the gun tube and reinforcing ring is inexcusable to this observer. Even if a steel breech band may not really be needed for strength, other considerations are paramount. In addition to the gas leak problem, we suspect that whatever welds were present to keep the breech ring in place, might fail eventually, closing off the vent.
The trunnions showed very poor welding technique, so the owner ordered them sectioned. Adding trunnions to a machined bar stock gun tube is always a challenge. The use of fabricated hollow tube for trunnions, with no evidence of closely machined seats to support the welds, has to be considered questionable at the minimum. No way would these trunnions be equal in any respect to original design.
The maker of such a cannon may argue that it is designed for blanks only and the strain on the trunnions is not great. Such a statement belies the greatest "sales" point of a "steel" gun tube.
Sooner or later someone will use full service loads and trunnion failure seems a good possibility. Damage to the gun carriage would be one expected result, and the possibility of injury to gun crew members, if a tube dismounted, cannot be ignored.
Owners of fabricated replica cannon, who were not completely involved in the manufacturing process themselves, should be aware of these potential conditions.
(About the Author: Matt Switlik is author of The More Complete Cannoneer, now in its third edition.)