@Vergift The maintenance is really only a small part of it; modern firearms are usually expected to fire a few thousand rounds before needing to be cleaned, so regular cleaning is less urgent than with a bladed weapon, where blood can cause the steel to rust. It's still a good idea to clean them on a regular basis, but it's slightly less of an issue if you miss a cleaning.
That said, the bigger issue is one somebody else mentioned elsewhere on this series and that's ammunition. If you don't have a factory that can churn rounds out by the thousands, making ammunition is a tedious process that can take a few minutes per round; and then you run into the issue of quality control. Some rounds might have too much powder or too little, resulting in stovepipes or failures to eject (which are exceedingly minor, as far as firearms malfunctions go and easily dealt with, but if you've got a beasty bearing down on you...), and then there's primers. They could be too hard, resulting in a light strike and the round failing to go off at all, or worse, a hang fire, where it goes off after a random amount of time.
All told, it's probably safer and simpler for everyone involved to just stick with medieval weaponry. At least with arrows, the worst you have to worry about is the wood of the shaft being too weak and breaking when you try to loose it.
