There are a number of scattered references to primitive firearms in AD&D 2nd Edition. There are also a large number of nerdy types such as myself who have tried to bring all of this information together in some sort of cohesive and intelligible manner to make sense of it all. This is going to be my attempt at such a data collection. There should be two takeaways from this: first, firearms run the risk of destabilizing a game quickly if the Game Master doesn’t keep a tight hold on how they are used and what the drawbacks are, and second the cost of these weapons should make them out of reach for all but the most wealthy and powerful of people. In a world of swords and crossbows the firearm represents an entirely new way of killing things that is both expensive and powerful. Their use should be by definition restricted to say the least.
Below are the various types of weapons that I currently allow. However, not everything is available everywhere. And while the weapon itself is expensive it pales when compared to the cost of finely made ammunition (for everything but the blunderbuss, that is) and the high cost and risk of either smoke powder or gunpowder. It takes a lot of effort to not blow oneself up attempting to use these things. Note the risks of misfires, number of attacks per round (which is dismal by any definition), and other variances that separate these from more traditional D&D weapons.
*This weapon is too heavy and slow to fire unless braced against a solid surface to aim properly. This can be done via a supporting brace, another person’s shoulder (cover your ears, mate), a large rock or anything of that nature.
**Whenever maximum damage is rolled, reroll the damage and add it to the original roll. This can continue indefinitely if a character keeps rolling high enough. For example a player that fires a Caliver rolls an 8 for damage. They then reroll and get another 8. So far that one shot has done 16 points of damage. They roll again and get another 8. Celebrations ensue. The fourth roll is a 3, finally ending the streak and giving a grand total of 27 points of damage.
The Blunderbuss is a unique weapon in that it shoots small bits of shrapnel and debris over a cone effect in the area in which it is aimed. All damage is delivered to everything inside that cone which is five yards across at short range, ten yards across at medium range, and fifteen yards across at long range.
All firearms disregard armor for the purposes of whether or not the attack hits. Dexterity bonuses to AC still apply, as do any bonuses against piercing style attacks. This renders firearms all but useless against certain opponents, such as skeletons that have no significant body mass to begin with or certain dragons that are immune to normal missile attacks once they hit a particular age. Firearms are considered nonmagical weapons for the purposes of hitting and damaging an opponent too, so unless the ammunition is blessed or enchanted that also limits their applications. The range of these weapons also makes them just as unreliable as normal missile weapons, suffering the same -2 penalty to hit at medium range and -5 to hit at long range. Yes the bullet is travelling faster but it is also a whole lot more inaccurate to begin with. Rifling hasn’t even begun to be a thing so the bullets fly pretty much at the grace of God towards their intended targets.
Bullets for firearms cost no less than 1cp each (blunderbuss benefit here from using anything sharp or dangerous that can be crammed into the cursed trumpet of doom, and garbage doesn’t usually cost anything). Gunpowder can be purchased for no less than 5sp per charge (not only does that add up but it becomes useless if it gets wet). Smoke powder is a magical equivalent to gunpowder, and while more expensive (5gp per single charge is a minimum cost) it functions even when wet.
All firearms run the risk of backfiring or fouling when used. On a natural attack roll of one they will backfire, causing 1d3 points of damage (non cumulative) to the user and the weapon will need to be cleaned before it can be used again. On a natural attack roll of two matchlock and flintlock weapons simply don’t fire at all (but another attempt can be made the following round). Wheellocks do not suffer this weakness and this is reflected in their cost. Matchlock users must also have on hand a source of flame in order to use their weapons, such as a slow burning woven match. These weapons work on a primitive fuse which is why their speed factors are so dismal.