Regarding firearm misfire chance and alchemical cartridges.

[Sparksol]

Firearms have a pretty simple and standard misfire rate, and alchemical cartridges tend to add a little on to that. That part is not in question.

Where my GM and I are seeing a difference in things is that he interprets that added +1 misfire chance from paper cartridges as being an additional +1 misfire for every alchemical cartridge used in that fight or until I take some time to clean out the gun between fights.

At the moment, my gunslinger is only 2nd level, but that will start adding up really quickly once we reach the point of multiple attacks per round.

Meaning my musket's 1-2 misfire in the first round with standard shot could easily reach a misfire chance from 1 to 8 (or more) in longer combats even now. He says this is reasonable given how I'm only aiming for touch AC most of the time, but is willing to possibly reconsider this if I can find some confirmation that the +1 misfire chance is not additive and simply a +1 misfire for that particular shot and not something making my gun gummed up and increasingly dangerous.

Can I get some help either way here?

[Ninjaxenomorph]

The cartridge only increases the misfire range when fired, similar to how a keen weapon would double the critical threat range.

[Claxon]

There is not going to be anythign definitive saying it's not a stacking +1, because if you read the description of alchemical paper cartridges there is nothing to indicate that it does.

He's asking you to prove something doesn't exist, ask him to prove it does. It simply gives increase the misfire range on weapons by 1 during each shot they are used. Otherwise it would stack until the weapon became worthless, because there are no rules for cleaning the gun to reduce the misfire chance from alchemical cartridges. If it required cleaning between shots using them, it would be mentioned somewhere.