wait--why can't fantasy have pistols?
it's fantasy, right....should fantasy have such limits/set rules?
don't forget that the Chinese were playing around with firearms about 300-500 years prior to the supposed timepoint of the King Arthur Myth.
I have no problem with it being Fantasy. And I have no particular 'Hook' on it having to be a Tolkeinesque setting. I have a problem with the logic of the whole thing.
The reason that technology advances at all is as a result of a specific need. You need something and don't have it, invent it. Something doesn't work properly, or is needed but is difficult to create and you develop technology to make it easier or better. Necessity being the mother of invention and all of that.
But fire arms and the like are not filling a need in a world with magic. Why would anyone mess around with something as messy and unreliable, not to mention dangerous as black powder, if you can chant a few words and shoot a missile unerringly into your target. why create a drum of powder that might explode and blow you to kingdom come, if you can cast a spell that is 100% safe for you, but really dangerous to your enemies.
Read A Clash of Kings in the section where Tyrion Lanister talks about the 'Liquid fire' and it's use in the battle to take Kings Landing. combat is messy. Why add to that chaos something that is just as likely to blow up in your face as strike your enemies?
Simply put, there is no coherence or reason why anyone would mess around with firearms where there are much simpler, safer and more efficient methods of getting it done available (ala magic).
and so until AK47s are invented, the magic practitioner is always going to be significantly more proficient in doing just about anything than someone using a firearm. And almost all of the 'Fantasy' worlds that people make games of today are absolutely Rife with magic use. Every peasant and their dog can crap out magic. So there is absolutely no need to create something that is just as dangerous to the user as it is to the intended target.
And remember, the firearms that the Chinese were using were VERY crude and nasty. A single shot and then throw it away, and that is assuming it didn't explode and cripple the wielder.