What caused the Ming army to be heavily equipped with guns, but still could not beat the bows and arrows of the Qing Dynasty?

There are many reasons. According to historical records, the most important thing is that the craftsman system was eroded when gunpowder weapons were widely popularized in the Ming Dynasty. The gun made is particularly easy to explode. Many frontline soldiers would rather not shoot than be injured by an exploding gun. In the Ming dynasty, the probability of being infected by gunshot wounds was high and the survival rate was low. Then there is the problem of powder. The powder is too poor. The range is very close, not as far as the bow and arrow.