Guns and Crossbow Expert?

[werescythe]

So there was a time I was considering running a campaign that would use the "Renessience" firearms from the DM rulebook. When I mentioned this to one of my player's he had asked me if I would allow the Crossbow Expert feat to work with firearms?

Thus I thought I might come back and just ask if any of you DMs have either done this or have feedback on whither or not this could unbalance a campaign where firearms are more common?

[braveheart]

I'm currently playing in a campaign where my GM allows us to get a custom feat "firrearm expert" which is just crossbow expert with the word crossbow replaced with the word forearm at every instance. So far it seems fine