Early firearms

Examples:

• Musket
  
• Blunderbuss
  
• Arquebus
  
• Bajōzutsu
  
• Belton Flintlock
  
• Bo-hiya (a mortar type gun)
  
• Dragoon
  
• Flintlock
  
• Matchlock
  
• Snap Matchlock
  
• Snaplock
  
• Wheellock
  
• Fire Lance
  
• Huochong
  
• Nock Gun
  
• Petronel (a one-handed arquebus)
  
• Tu Huo Qiang (a loaded stalk of bamboo, but still lethal to its target)
  
• Miquelet Lock

This covers quite large number of firing mechanisms: wheellock, flintlock, matchlock, and others.

Although most were muzzleloaders, there are some early instances of breech-loaded firearms even as early as 15th century, these are still in use in modern weapons, though mostly in hunting rifles and cannons.

All early firearms were handguns, rifles or shotguns.

All early firearms were susceptible to malfunctioning more so than your average modern firearm (though some of the worst malfunctioning guns are modern ones). However, human error greatly contributed to the risk of malfunction.

All early firearms were generally less accurate than most modern firearms. Longer barrels helped. Rifled barrels are an element of modern firearms. It is notable that using modern balls and smokeless powder in ancient firearms can increase their accuracy and range to the point that they are competitive weapons when used alongside modern firearms in target shooting events.

All early firearms can only be fire less frequently than most modern firearms. There was not much that could be done to speed up reloading. The only exceptions being superposed load firearms (also called stacked charges), guns with multiple barrels (pepperboxes with single fire mechanisms), paper cartridges, and percussion caps. The first two of these exceptions produced reliability problems and were only rapid fire for several shots. Once they were empty, firing and reloading was just as slow as any other. Percussion caps had their advantages but they were only faster when the firearms operator was skilled, practiced, prepared, motionless, and relaxed (the lasts two being difficult to come by in combat or on horseback). Paper cartridges usually amounted to a convenient way to carry just the right amount of everything to load a gun once. They would be opened (biting was the quickest) some power poured in the flash pan and the rest down the barrel (so there was still a problem with inconsistent loads due to human error, but the margins were tightened up considerably, and they could be no overloading). The leftover package and ball were then rammed into the barrel, cleaning it somewhat. This sped up loading considerably but only saw sporadic use. There were also paper cartridges made to be inserted as-is (amounting to a paper bullet except the ball was lead) then lose power or some other flammable element was placed in the flashpan separately. This second form of paper cartridges was even rarer than the other. Paper cartridges are pretty much for early modern firearms anyway, and not so much for pre-modern ones. Paper cartridges could be waxed or lubricated and added the advantage of sealing the load and making the firearm fairly moisture resistant (but did nothing to protect the flash pan from moisture).
But the Kalthoff repeater solved all the problems with the fast loading technologies. It used 3 different magazines. One for the balls, another for the power, and one more for the primer. It was breech loading. It had a sliding mechanism operated by the trigger guard that deposited the ball, powder, and primer, and cocked the wheellock (later models used a flintlock). It could fire up to 1 round per second for 6 rounds. Then the three cartridges were ejected and replaced by hand in a 1 second operation for a final tally of approximately 51 rounds per minute sustained firing rate. It was also among the safest of ancient firearms, the mechanisms kept all the power perfectly isolated from the flame until it was safely loaded. No danger of even the most incompetent operator ever accidentally igniting the powder. Dispite all the advantages, it was extremely expensive operate and more prone to malfunctions than its contemporaries. Minor damage (through even intended careful use) to any single part of the gun rendered it unusable until a blacksmith could repair it (interchangeable parts for all practical purposes are a modern invention). A simple jam ruined the gun. This was the first example of a repeating rifle and was extremely rare.

The Miquelet Lock gun had an adjustable clamp so as to use flints that could vary in size by a considerable margin. In addition to the flint being useful even after tremendous wear (like pencil eraser still works as it become smaller), a replacement flint need only to be roughly rather than precisely shaped. All the major parts of the lock mechanism were detachable and relatively easy to replaced. Almost interchangeable parts. Spares could be carried and quickly installed. Additionally the flash pan was covered and could remain shielded from rain during loading. Rain was not a guaranteed malfunction the same as it was with contemporary guns. The flintlock came later and had some of the same advantages, but also gave up the easy replacements.

Hand Cannons have their own group.
The following are modern firearms and should not be counted as early firearms:

• Howdah pistol
  
• Anything invented after the Second Boer War