Someone wanted firearms in M and B Warband?
1. Launch Warband
2. From Launcher, go to config and tick the box that says enable cheats
3. In campaign, press control ` and in the command line box that pops up, type CHEATMENU
4. Camp
5. Go to the CHEAT! option
6. Click find an item.
7. Every item in the game is here, including modded items. You will need to buy them from this menu, so use ctrl x to get 1K denars until you have enough.
8. Somewhere inside all of those pages (at least for me, as I have Floris which adds 1.2K items) will be firearms. You'll need cartridges for ammo.
9. They're fairly sucky IMO, especially compared to crossbows.
10. You also lack the ability to get any better with them because AFAIK they aren't tied to a skill.