Unlike Polofox, who I posted earlier, the Italian missionary Martino Martini, the author of this history of the Manchu conquest, had actually been to China. He has little to say on the types of arms used, only this:

Pages 16-18

But the City [Leaotung] was defended by exceeding many men, who generally were all armed with musquets: the Tartars had nothing by their Scymetars, with Bows and Arrows, which they discharged with strange dexterity & Art. But because they chiefly feared the musquet bullets, they resolved by a Stratagem to make that unknown Instrument less hurtfull to them than their Enemies did imagin. For the Tartarian King commanded such as made the first onset, to carry a thick hard board for their Shield, which was as good to them as a wooden Wall; these men were seconded by other Companies who carried Ladders to climb up the Walls; an the Horse came up in the Rear. In this manner he set upon the City in four quarters, and received the discharge of their Musquets against his Wooden wall; Then in a moment the scaling ladders being applied, before they could charge again, they were upon the Walls and enterd the City; for such is the quickness and nimbleness of the Tartars (in which they excel all Nations, and idn which also they place their chief art) that in a trice, they either prevail in their Designs, or retire: and the little skill the Chineses had in the use of Musquets, was no small hinderance to this War. For the Tartars quickness and nimblenes not giving them time to charge again being astonished with the suddain inundation of armed men, they presently fled which way soever they could…

The Ming seem to have had a shortage of bullets or cannon balls, at least in Beijing. In 1644 Beijing, the Ming capital, was besieged and captured by Li Zicheng’s rebel army. Shortly after crowning himself Emperor, Li fled the city to escape the invading Manchu army. This is the second reference I have seen to cannons being fired empty:

Page 85

But, however it was, these Pilferers came in a short time to besiege the Royal City of Peking. There was in that City a vast Garrison, and as great a quantity of Artillery; but on the Quarters upon which the enemy made there assault, there was none charged with Bullets, but only with Powder.

The second comes from the scholar-bureaucrat Liu Shangyou, who had arrived in Beijing just a few months before the siege:

On the 17th [of the 3rd month, April 23] artillery fire shook the heavens, and I knew the bandits had reached the foot of the city walls. The guns on the walls were fired empty as often as not– for lack of ammunition. Below the walls the bandits also relied on artillery for their attack; each firing of a cannon was sure to collapse a roof or topple some tiles– anything that got in the way was smashed. Their ammunition was shaped like a man’s thumb– keen and shiny, hard and slick, really effective.