Are you talking more about civilians owning firearms/having licenses to own firearms, or more about the change in the military? Civilian firearms were never really a large 'thing' in China outside of use by police, security personnel, and the military, as even now within the PRC firearms are only authorised to groups (e.g. hunting groups, wildlife research & management). A man would thus never have owned a pistol or a musket unless they were part of the authorised groups above.

Before the 19th century, the majority of Chinese armies were still primarily sword/bow/etc. rather than guns - while matchlocks, light mortars, and various (relatively) primitive gunpowder weapons were also seen, they were not as common. The First Opium War (1839 - 1842) was the first major conflict pre-modern China had with the West, where the Qing soon found they were severely outclassed by the superior weaponry of the British. Chinese ships and weapons, especially, were found to be of no use against the heavily armoured and equipped British ships. After their defeat in both the first and second Opium wars, in the late 19th century China began to do the first overhaul of their military, essentially transforming it into an early version of the modern military systems you see today (e.g. enlisting artillery and engineering groups, dividing the army into brigades, adopting different tactics).

Due to China's relative 'sheltered' nature, unlike Japan, the clash between sword/spear and gun happened occasionally but not significantly until the Opium wars. The Japanese had this as exposure to the West and free trade/production of matchlocks started much earlier due to civil wars, but China had a significantly more 'closed doors' approach to foreign relations, restricting trade to certain cities and heavily favouring Chinese merchants - another reason why the Opium wars began.

Sources:

Western Imperialism and Military Reform in Japan and China - Hevia, J.