Actually, the metallurgical composition of early steels wasn’t as big a detriment as the physical mechanism by which it was made. Steels were smelted in small lots, or hammered, or a combination of both. Usually there were inclusions, and the more care that went into making the steel the fewer the inclusions. Almost all early steels had some though, and these are the greatest source of weakness. An included contaminant could cause an early failure, or it could lead to a fracture later in the life of the firearm. If it reached the surface, rust would form in the vicinity of the impurity, which could lead to a fracture.

One of the biggest advances in industrial technology was the invention of the electric smelting process. Now relatively clean steel could be produced in large batches. Modern steel lacks the inclusions that caused so much trouble in early steels. Modern ordinance steel, even if quite mild, is far superior to the steels in use in the 19th century.