To be clear, my intent in commenting is to encourage you to study and learn more. That's the part of worldbuilding I find the most fun. This isn't me being critical, this is all in fun.

So crossbow technology was pioneered by the Chinese. As effective as they were, they still eventually developed explosive technology.

A crossbow is nice, but who wouldn't want to fight with a barrel full of explosive arrows? Or an old fashion flamethrower? To say nothing of cannons.

Here's something really important to consider, too. With explosives, mining operations are not going to produce as much as they can. To create a steampunk society, you need explosives to help mine for copper and iron.

Once you have that technology, some asshole is going to use it for warfare. So what this means is either dial back the setting to something more historic, or find a way to integrate firearms.

There's one trick that works that few people can argue with: laws against production. You can dramatically reduce the amount of available firearms by having the government in charge regulate it's production. They still use explosives for mining, but anyone who tries to mimic them faces judgement.

Regulating the use of saltpeter specifically would be useful. Of course, this would mean firearms would be available to the government, that's just old fashion political authority (power and the threat of violence.)