From a mechanics standpoint it's just not appropriate. You're just as likely to one shot another player as you are to one shot yourself in Barovia's intended level range.
Even if we ignore those issues, you wouldn't be able to afford it. The lowest quality pistols are several hundred gold and as a lvl 2 PC you just don't have that. Even then you still need powder and shot which in any usable quantity is going to me more expensive than the pistol itself.
Last, from a point of lore, the flintlock represents a picnnacle of scientific and engineering achievement in the more developed areas of the core. It just not appropriate for Barovia. It also presents one of the attractions for going to dementlieu. It's not really fair to cheapen that niche.
If you want to make a group of gun runners to trade in an illegal market in Barovia by all means go ahead. I've done it before and it's lots of fun!