Cannon wrought iron

The problem was that cannon were then made with cast iron, a form of iron that contains relatively large amounts of carbon. Cast iron is very hard, but it breaks very easily. The only substitute available for cast iron at the time was wrought iron, which is nearly pure iron. Wrought iron, however, was not suitable for making cannon (or almost anything else) because it was too soft. 

On a cylinder of aist iron (the best material for the inside of a cannon) shrink a layer of wrought iron rings with morlemtn tcn.sion these, witli tJio < ylin-dev should form about one-half of the thickness ol the gun, Kig. 4. Banda of steel should now be wound spirally in alternate layei s to the requiree wound while heated directly from a furnace prepared for the purpose, and the tension in-... 

Brass guns are said to have been made for the Sheriff of Northumberland in 1385 but guns of this alloy soon proved too weak and were superseded by wrought-iron and cast-iron cannon (pp. 274, 2,77). ... 

In the fifteenth century cannon were made by hooping wrought iron bars together Mans Meg, in Edinburgh, made in 1455, is a noted example. 

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