In the late 1700s, China enjoyed a large trade surplus with the west, exporting tea and porcelain, but demanding silver in return as there was little demand for western exports. This led to the Opium Wars, in which the superiority of British weaponry was a decisive factor. Why, prior to the outbreak of hostilities, had China not sought to import western armaments as part of its trade with the west?
Necessity, as they say, is the mother of invention. Simply put, the Qing did not expect to fight a war with a Western power, and so accordingly did not place significant stock in purchasing arms of equivalent quality. As I note in this past answer on Qing armies this past answer on the Qing fleets, when armed encounters with foreign militaries became more expected, the Qing did quite rapidly seek to increase their use of foreign equipment.