(off topic) Lightweight weapons for Victorian fantasy setting

A bit off-topic, but given how many fans of weird weapons we have here I 
hope that people may be able to help a little.

The next release of my Forgotten Futures RPG is a quasi-Victorian 
fantasy setting with steam technology and a separate dragon nation, 
based (with permission) on Jo Walton's _Tooth and Claw_
http://www.zorinth.net/bluejo/books/dragon/dindex.htm

While it's nearly complete, one of the things I haven't addressed in a 
lot of detail is the Dragon military's equipment and tactics. Basically, 
while they do have gunpowder (in paper cartridges) and percussion caps 
they (and the Yarge [humans]) don't yet have breech-loading weapons or 
all-in-one cartridges. I don't want to change this. They can easily fly 
carrying e.g. a very large rifle and ammunition, but anything heavier 
than say a sheep or a small cow is going to be a problem for an 
individual dragon.

A typical dragon soldier carries a rifle, and may be able to breathe 
fire though that isn't universal. He also has claws, fangs, etc. But 
given that they are hugely outnumbered by humans, and much more accurate 
with their guns when they aren't flying, getting close enough to use 
these weapons without getting shot isn't easy. They need some bigger 
guns.

My basic idea for an air-trans****table heavier weapon is a squad of 
dragons carrying a lightweight cannon that breaks down to several 
components (the barrel is obviously the heavy one), plus the wheels, 
frame, ammo, etc.; they have to land to use it, of course, but it's very 
good for skirmi****ng.

Heavier guns are drawn by oxen etc. and can only be moved on the ground.

What I'm looking for is another dragon-****table weapon, something a 
little more exotic - not bombs or grenades, I think, they don't really 
have accurate enough fuses or detonator caps. Something like Congreve 
rockets might be a possibility, any other suggestions?
-- 
Marcus L. Rowland             http://www.forgottenfutures.com/
LJ:ffutures     http://homepage.ntlworld.com/forgottenfutures/
   Forgotten Futures - The Scientific Romance Role Playing Game
   Diana: Warrior Princess  &   Elvis: The Legendary Tours
   The Original Flatland Role Playing Game