mxyzplk
Explorer
I don't put guns in every campaign world, but I don't see why not have them in many. I wrote these firearms rules for Pathfinder (free download from RPGNow). They have misfire and slow reloads but have exploding damage. The way they're designed they're not really meant to be someone's primary weapon (as in shooting a gun every round for sustained DPS) - just like early firearms IRL, they are used for opening or closing punches by people who are generally doing something else or volleyed by large units. I've been using them in a long term pirate campaign and they hit the right balance - some characters bother with them, others don't. They're OGL, feel free and use them if they are useful.
I almost never buy the "magic not science" line. Very few campaign worlds have magic so pervasive that anyone can use it. If not everyone can use it, then those other people will be happy to go for "next best". If all castles aren't built by magic, and magic doesn't replace all the alchemical items, or indeed replace normal missile and melee weapons, then it's a nonsensical claim. Is a crossbow not technology? Is a longbow not technology? Previous centuries would strongly disagree with you. The main reason gunpowder is not accepted in D&D is a legacy concern from Gygax & friends that it would be unbalanced somehow, and then justified in odd ways. And you do have to worry about the more explosive applications of gunpowder, but at least with early black powder it was not nearly as easy as "toss a match and it explodes like a ton of TNT" like you see on the movies.
I almost never buy the "magic not science" line. Very few campaign worlds have magic so pervasive that anyone can use it. If not everyone can use it, then those other people will be happy to go for "next best". If all castles aren't built by magic, and magic doesn't replace all the alchemical items, or indeed replace normal missile and melee weapons, then it's a nonsensical claim. Is a crossbow not technology? Is a longbow not technology? Previous centuries would strongly disagree with you. The main reason gunpowder is not accepted in D&D is a legacy concern from Gygax & friends that it would be unbalanced somehow, and then justified in odd ways. And you do have to worry about the more explosive applications of gunpowder, but at least with early black powder it was not nearly as easy as "toss a match and it explodes like a ton of TNT" like you see on the movies.