i think yes, but nothing modern however. i beleive guns in the classic dnd would be more along the lines of flintlocks, automatic crossbows, bowguns, and miniature cannons.
all of course having their pros and cons (ie autocrossbows do very little damage but roll 3d# or how mini canon does massive damage and can destroy walls but holds only 1 shot and takes 3-5 turns to reload) guns would be very expensive too around 50gp for a good flintlock, ammo would be a cheaper 30 silver for 50 shots (in this case gunpowder for your new flintlock). i would like to see all of your opinions on this however.

...I've got some notes on this, somewhere, that I scribbled down when I was considering running Smuggler's Moon as a "rules-based" game... Given the theme of the game, of course, we're working with flintlock/wheel-lock/matchlock type firearms (and cannons... can't forget the cannons)...

There was something about weapon proficiency trade offs (character classes who usually start out proficient with crossbows, for example, get those proficiencies swapped for pistols, etc....) and, of course damage, range, and similar stats for the weapons themselves played in there, somewhere.

Got some running around to do today but I plan on lingering around the Inn later tonight... When I get home and can rifle through my notes, I'll be sure to post up what I've got here, for you.

If I were you, I'd make such weapons VERY powerful (which they are in reality.)

I'll go through your examples one by one:

Flintlocks These should deal medium-high damage. However, don't let your characters near one without the disadvantages of early firearms: cleaning it, using gunpowder, and price. Also, make it a difficult weapon to handle, AKA give them a hell of a penalty for using them unless well-trained. Something else to consider is that in a classic DnD setting, not everyone has a concept of how to use a gun, particularly pistol flintlocks. In the 21st century, kids as young as 5 get the concept, whereas in a world where guns are quite rare, there won't have been the imprint through socialisation.

Autocrossbows Same as crossbows, but I'd suggest a little less damage (not much, but a little less) and a penalty to each shot, say -1. Make the bolts necessary more expensive, too. However, give them a Charisma bonus for badassity ^^
Oh, and reload time, maybe? The mechanism may require a lot of winding and fiddling to get into place.

Bowguns Don't have a clue what they are. Tried looking up on Wikipedia, it gave me "Crossbow".

Hand-Cannons Give them huge stopping-power and high damage, but don't go overboard on the damage. Make them highly inaccurate at longer range, using a scale (I dunno, every 10 feet is -1 to hit?). Make them VERY expensive, and make your NPCs all tell tales of their power and usefulness... but also about how they can go wrong.
Write yourself a possibility table with some "fumbles", for example damage to the cannon with misfire, or any other hilariously dangerous bad events. Have the cheaper variants be very unstable.

In fact, make gunpowder pretty unstable unless you buy the Mega Mega High Quality Yet Expensive (tm) type.


I hope these ideas from someone who knows nothing of firearms help.

...if you do use firearms, I'd make them "rarish" or, better yet, make other concessions to balance things out (i.e. whittle back the potential for magic, etc)... As I said... more on this later... gotta run before the wife scowls me into submission.

bowguns are similar to crossbow but fire various types of ammo that only they can (ie certain bowguns could use a shot that does water damage), even to make multiple attacks with one bullet (ie a bowgun that specializes in underwater combat could shoot 3 sub shots but uses only one ammo),complety customizeable you can change stocks frames and barrels to fire many different kinds of ammo (although maybe not as effectivly) and would be almost (if not as or more) expencive than mini cannons.
also the bow gun is an idea from a video game series called monster hunters, but it sounded like something you could put in a dnd game.

Forgotten Realms include firearms based upon 'smokepowder' (~gunpowder). you need your firearm, a powder horn, and the bullets your firing. It refers to the Dungeon Master's Guide (3.0), page 162. It explains utilizing 'tech' for gun/grenade devices in dnd setting (usually a gnome invention). and firearms are typically classed under Exotic weapons, for good reason (as Darren mentioned above).

Cheers!

-TO, the shameless FR fan

they really do

anyway some mishaps i thought up for hand cannon
-cannon doesnt have enough powder,drop cannonball on your foot,too much gunpowder roll a 16 or your cannon is destroyed roll16+ and it just loses 25% durability luck also helps,accidentally shoot the supporting pillars of the building your in(oops),someone (through skill or luck) manages to plug the cannon before you fire:better hope your cleric can cast revive.

bowguns are useful (and diverse)
bowguns can be light,med,or heavy
bowguns can use many kinds of ammo (pellet[shotgun type ammo],peirce,exploding ect.)
bowguns can use magical ammo(water,fire,lightning,poison,dragonfire[closerange])
bowguns are uber expencive(200gp for the weakest, least expencive one that can only use lv1 non magical shots)

If you're into 2e, Combat and Tactics introduced a system for firearms. They were very powerful, being able to shoot through plate armour and do a lot of dice worth of damage, but every shot risked damaging the weapon in some way, as is per a typical risk of using black powder. Furthermore, they weren't common, and were highly expensive to acquire.

They were used during a Renaissance Age of technology, though, so not your standard Dark Ages setting, during which if somebody HAS developed black powder, they'd be even more expensive and difficult to acquire!

Basically, I guess what my above point gets at is to be careful if you plan on introducing firearms into a setting. There's a reason metal armour went on a massive decline when it had about as much ability to stop a bullet as a cloth tunic did. Be prepared for big changes to the tech level of a setting if guns become popular.

but we could have special armor that could stop bullets or atleast reduce the damage of one anyway. but also i would have made the more powerful guns rarer anyway not to mention how expencive they would be.

They sound like a pretty bad idea to me, actually. Where they work as a concept in a video game, here they'd get in the way. If they're THAT adjustable and customisable, then they're the perfect tool, leading to one of two scenarios:

- Everyone who gets enough money to buy one, or get their hands on one, becomes an adventurer and owns the world.

or

- The big villains get them, train well, and every adventurer EVER? Gets killed.

EDIT: It just sounds broken. I'd stick to the simpler gun-style weaponry.

but remember the power to stop a horde of dragons with your party would be worth the millions of platinum you would have to spend . and i think it was the way i put it in that made it sound op not the idea itself (i mean 200gp for a weapon that only does 10 damage and then another 100gp for a sizeable amount of the weakest ammo that only does 5 damage and no special effects other than it wouldnt feel very good in your eye) doesnt sound too op now i hope :-/ .

EDIT:also all the parts effect eachother using the weakest stats of each part so not all customizations would be very good (even though said parts make it look ba)and the requirements for it are rather high if put in a dnd game using a high amount of str and dex to use not to mention lv and skill req

Ok, that deals with that, then. But another thing springs to mind: it's a fun mechanic, I'd suppose. But you're already augmenting the basic system with firearms. Is it perhaps overkill to add this too?

Maybe, maybe not.

i suppose it all about how you go about making your dnd game as involving and fun as possible and what would and wouldnt work well in a fantasy game. such as made up weapons or customization for even the most simple or common items in the game. however i have noticed that more detail and interactivity makes any game more fun.

(not sure i explained it in a non offencive ,understandable way)

and tomorrow ill post another topic that should punch your brain into shape with another great question

I guess so... but, not meaning to pick holes, but then the wielders of other weaponry will feel shortchanged. Possibly.