Concept: Alternate gun mechanics
Tested in: Various Eight Arms campaigns
What it is: D&D assumes a standard medieval fantasy setting, and Pathfinder assumes a medieval fantasy setting that likes to pretend it isn’t standard. The Eight Arms world time-advanced that setting to a Victorian or Edwardian era, with trains and factories and terrible labor laws. By the early 1900s swords and full plate weren’t the technologies of war they once were. To literally put the era in the PCs’ hands, I felt we needed some sort of gun. But Pathfinder didn’t have guns, not yet. The Eight Arms and the Shadow Invasion predated Ultimate Combat and its firearm rules by three months. We had to make our own.
The Eight Arms firearms are glorified crossbows. By these rules a pistol is a light crossbow, almost exactly. A rifle is a heavy crossbow with slightly higher damage. A revolver is a repeating light crossbow, but it’s a martial weapon because I have no earthly idea why it takes an Exotic Weapon Proficiency feat to figure out how to pull a lever. There’s also a hunting rifle, and it’s basically the normal rifle with a faster reload time. That’s pretty much the extent of it. We don’t have Pathfinder’s rules for misfires, gunpowder, or touch attacks within the first range increment, and all the prices are scaled down so a low-level PC can afford them.
What I wanted: Firearms are an accessible part of the world but not its focus. Players can use them in a pinch, and they don’t overshadow the swords-and-magic combat that makes Pathfinder work.
How it went: In the context of what I wanted, the gun rules have been an unmitigated success. PCs use them as sidearms, falling back to them when something prevents them from taking their normal class-based actions. When an enemy pulls one out, the players don’t have to drop everything to deal with it because they know its presence doesn’t automatically indicate a master marksman. But somebody can specialize in guns if he or she wants to, and they’re not limited by exorbitant costs or a dearth of ammunition.
In the years since I made this rule we’ve expanded on it. A player brought a gunslinger to the table, and the class worked with these firearm rules after some very small modifications. Another player used this concept as a base and created his own personal minigun, a glorified bow that sprayed an alarming number of attacks at enemies. I’ve not heard anybody ask to use the Pathfinder firearm rules. In a fact, a few players have said they prefer these to the official rules, mostly because the official rules exist in a weird balance space; when firearms work, they’re this close to unfairly good, and when they don’t, they’re this close to unfairly bad. By tweaking and reskinning crossbows we treat guns as a normal weapon instead of a lottery.
What I learned: When you add something to the rules, make it fit the system instead of the other way around. Be wary any time you have to add several new supplementary mechanics (gunpowder, misfires, first-range-increment touch attacks, scatter targeting, etc.) to allow one new thing. It can work, but you may be doing far more work than you should.