Here's the post I promised in the comm profile!
There were several types of firearms available in the 18th century. All of them would be flintlocks, meaning the powder is ignited by a spark from a flint.
This site gives a good overview of how a basic flintlock works.
The POTC films don't stress how long it takes to reload, but it's a fairly lengthy process even if you already have a
paper cartridge. You have to tear off the end of the cartridge (generally with teeth), pour some of the powder into the pan, close the pan, up-end the gun, shove the rest of the cartridge in the barrel, pull out the ramrod, ram everything down the barrel, replace the ramrod, cock the gun, and fire.
Handguns
Pistol -Jack and Barbossa each carried a
pistol. This is your basic handgun, firing a round lead ball - accurate to about 30 yards, max. You're not going to be shooting at another ship with your pistol, this is a weapon to use when you're boarding.
Blunderbuss -
This weapon is less accurate than a pistol, with a range of maybe 10 yards. With a barrel that
flares outward, it's meant to spread shot or shrapnel across an area and would be a good deck-clearer.
Long Arms
Hand Mortar - The
hand mortar is the weapon Marty fires in AWE that launches him backward. It can fire grenadoes (a cast iron ball full of powder) or grappling hooks.
Musket -
A musket shoots a lead ball or shot and has a range of about 80 yards. Generally larger caliber than a rifle.
Rifle -
A rifle is similar to a musket, but the barrel is rifled (has spiral grooves cut into the inside of the barrel). This rifling makes the bullet spin, which gives it stability and in turn, accuracy at greater distances. It has a range of 100 to 120 yards, depending on the skill of the shooter.
All of these weapons can only fire one projectile before having to be reloaded. The only way to fire more than once without stopping to reload would be to have a gun with more than one barrel. Double- or multi-barreled guns would be rare, but Pintel has a double-barreled pistol in CotBP, and Jack starts out with it (or a similar one) in DMC. If you notice, he shoots the bird on the coffin and then tries to shoot the monkey using the same gun.
Hope you found this informative!