What was the cannon like in Hongwu period?

When the south wall of Taiyuan, Shanxi was demolished, it was found that there were three doors, all of which were hidden in Shanxi Art Museum.

The gun body is straight and short, with a caliber of 2 1 cm and a total length of 1 m, and the words 19 are cast on the front of the barrel: "Ming Hongwu was cast by Pingyang Wei in the Ming Dynasty for ten years." There are two pairs of ear handles in the middle, which are square and long 16 cm. They should be used for operation, not for adjusting the shooting angle. Tail slightly closed, the whole body three times. This kind of gun has large caliber, thick tube wall, much better elastic performance and range than the bronze spear in the early Ming Dynasty. It was the most powerful heavy artillery at that time. The low cost of casting guns with iron creates conditions for mass production of guns. However, iron gun casting is easy to produce defects and lead to explosion, which requires high casting process. Pingyangxu, the foundry of this gun, is located in Linfen, Shanxi Province, and has been a famous iron smelting center since the Tang and Song Dynasties. The casting of this kind of iron gun shows that at the end of14th century, China's gun manufacturing technology has been among the advanced in the world.