Please help me nail down some Pre-Renaissance Firearm stats...

[Azzy]

Here's what I got so far. Keep in mind that most of these weapons shouldn't be as good the Renaissance firearms in the DMG (pp. 267-268), but should be equitable should a player choose them over (or in addition to) a normal weapon. The Reload property in in the DMG.

Fire Arrow. This weapon is a rocket propelled arrow fired from a metal barrel.
Fire Lance. A fire lance is little more than a normal spear or lance fitted with a tube filled with gunpowder and pellets or debris. While the fire lance can be used as a normal spear or lance, the tube can be lit, firing its shot and spewing forth a spout of flame up to 15 ft.
Firecaster. This primitive flamethrower can project a line of burning alchemist’s fire 30 feet long and 1 foot wide. Each creature in the line must make a DC 12 Dexterity saving throw. A creature takes 1d6 fire damage on a failed save, or half as much damage on a successful one. On a failed save, the target takes 1d4 fire damage at the start of each of subsequent turn. A creature can end this damage by using its action to make a DC 10 Dexterity check to extinguish the flames.
Hand Cannon. The hand cannon, or handgonne, is composed of a large bore metal barrel affixed to a wooden shaft. To weapon requires the user to ignite the gunpowder in the touch hole with a slow match, burning stick or coal to fire its cannon balls.

Name Price Damage Weight Properties
Martial Ranged Weapons
Fire arrow 25 gp 1d8 piercing 5 lb. Ammunition (range 40/120), loading, two-handed
Fire lance 25 gp 1d6 piercing & 1d6 fire 7 lb. Ammunition (range 15/—), loading, special, two-handed
Firecaster 200 gp 1d6 fire 5 lb. Ammunition (range 30/—), reload (5 shots), special, two-handed
Hand cannon 150 gp 1d10 piercing 14 lb. Ammunition (range 30/90), loading, two-handed
Ammunition
Fire arrow arrows (10) 50 gp — 2 lb. —
Fire lance shot (10) 2 gp — 1 lb. —
Firecaster alchemist fire 250 gp — 5 lb. —
Hand cannon balls (10) 6 gp — 5 lb. —

Sorry for not table formatting... I'm not sure how to make it pretty for the boards.

 

[Celebrim]

So, this was developed for 3e, but this is my stats for a hand gonne:

14th Century Hand Gonne: Dmg: 1d10+1, 19-20/x3; Range Increment: 25’; Penetration: +3; Accuracy: -1; Reload: 2 full rounds; Weight: 8lb.

Penetration means the armor bonus of the target is reduced by 3 (which negates armor for 5e purposes). Accuracy -1 means that you have an inherent -1 penalty to hit. The weapon can fire every third round.

Make of that what you will.

Fire arrows should be considerably less accurate than ones fired from bows. They mainly saw use for starting fires, and they had the advantage of being able to be fired in large prepared volleys. They are mainly siege weapons targeting areas, not individuals, and I'd give them a -4 penalty to hit or something of that sort.

There is also a 'fire arrow' head that can be attached to a normal bow fired arrow, mainly again for starting fires. They never replaced normal broadheads for anti-personnel use and should have several drawbacks in addition to cost.

Your description of a 'Fire Lance' is appropriate for early fire lances, but the damage you assign to one is more appropriate for the latter specialized weapons that replaced the lance point with a metal tube. Earlier weapons should do less damage, say 1d4+1d4 or even 1d3+1d3, be attached to lances or spears, and give the wielder a -2 penalty to employing the main weapon owing to the weight that they add. Up to two can be attached to a lance or spear.