For almost two hundred years the flintlock firearm was the state of the art for the military around the world. First developed by Marin le Bourgeoys for King Louis XIII of France around 1610 they continued to be refined and developed until the mid-19th century when percussion caps became more the norm.
The flintlock pistol was normally used in conjunction with another weapon, sword or cutlass and would fire one shot before having to be reloaded. They ranged from six inches up to twenty and were mostly smooth bore. Effective and powerful in the short-range their greatest deficiency was that time it took to reload. For those that have never done it here are the steps:
Load the flint into the lock.
Half-cock the cock
Pour the proper amount of black powder down the muzzle
Tamp it down
Wrap the ball in a patch, usually linen or cotton
Put the ball in the muzzle
Tamp the ball and power down with the ramrod
Prime the flash pan
You are ready to fire!
Now imagine that in the middle of a fight, probably not going to happen which is why you would normally carry more than one.
Not only is the load process time-consuming, but the actual flick that makes the spark can sometimes be an issue. They wear out, and if not produced right is just plain ineffective. Of course, keeping your powder dry was a major issue. Even when it was you would have to constantly clean the powder residue from the weapon to keep it functioning. Since most of the pistols were made by hand the parts were mostly not transferable from one to another. So if something broke, you may be out of luck.
Still, though they were good weapons and were integral in not only the military but taming the new frontiers found on the American Continent.