[KevinJ]

I used the following rules for my Goranth (non-Cidri) campaign.

The HACKBUT is a large matchlock musket. It fires a single ball for over 70 hexes. It is considered a missile weapon, doing 3+3 dice damage. It is very clumsy; it takes 2 turns to ready and 12 turns to reload and ready after firing. the Hackbut can be aimed to increase accuracy, +1 to hit per round spent aiming, up to +3. Anyone without the GUNS talent is at -4 to hit and gains no bonus from aiming.

The CALIVER is a short barreled matchlock weapon designed to be fired with one hand. Once fired it is a club. It fires a single ball to a distance of 60 hexes. It takes 2 rounds to ready the Caliver to fire and the shooter makes a 3/DX roll when firing to keep hold of the weapon, failure means the caliver is dropped. It takes 6 rounds to reload a Caliver.

BLUNDERBUSS is a short barreled gunpowder weapon with a large bore and a bell shaped muzzle. When discharged, it affects every target within a triangular area 10 hexes long. Its apex is the hex the blunderbuss is pointed into, adjacent to the user.
Every target in the blast area is affected by the blunderbuss if a straight line between the center of his hex and the blunderbuss hex passes through no obstacle or occupied hex. Figures affected by the blunderbuss must make a saving roll (4/DX); if they miss, they take (1d+2) damage from a hail of rocks, rusty nails, broken glass, and other junk. The user of the blunderbuss must make a saving roll (3/ST) to avoid falling down from the recoil. (If, he/she does not have the GUNS talent, -4 ST for this roll!)
A blunderbuss takes only 1 turn to ready, but 12 turns to reload after firing.

The HARKBUS is a very large gunpowder weapon, a bit to large to use without resting it on something. There is a hook near the muzzle that allows the Harkbus to absorb most of the energy from firing by hooking the weapon on the top of a wall, a windowsill, or a tree branch. The bore on a Harkbus makes a Hackbut look like a children’s toy, hence the hook. Resting the weapon reduces the ST Min to 8. Normally only used for defense of a fortified position.

There is always the chance that a given charge of gunpowder will be bad. Before firing any gunpowder weapon, roll 2d. On a roll of 11+ the gun does not fire. Of you bought very cheap gunpowder, the GM may make it a roll of 9+!)
On a roll of 18, a gunpowder weapon explodes. The explosion does damage like a grenade (see below), except that there is no significant concussion effect.

Weapon................ST..DMG...Wgt....Cost
Blunderbuss (AoE)..4...1+2....1.5.....$200
Caliver...................8...2+2.....2......$300
Hackbut................8....3+3.....5......$500
Harkbus...............12.....5......10.....$1100

For Cost comparison:
A Broadsword is $80.