Yeah, I'm all for it.
And fantasyworks just fine with experiments under (or was it in? I'm not sure) squash courts. See the Discworld, where the wizards split the thaum, producing unlimited power. No, it's not exactly what you mean, but that's the best example I could come up with for tech and magic not being mutually contradictory.
And gunpowder firearms are far from fission, I can assure you. They fit in fine with fantasy, too, just a lot of authors don't like them, so they make up stuff like magic interfering with technology.
And anyway-- yeah, you have guns... BUT SO DOES EVERYONE ELSE. Including, I suspect, Hobbes. And I doubt the Undead and the Balverines and the Sprites and all will be much easier to kill with guns than swords and bows, simply for gameplay reasons. And some of them, like the rock trolls, wouldn't be any easier to kill with firearms unless by "firearms" you mean "big keg of gunpowder with a fuse stuck in it".