Feeling the Groove…
Firearms for a very long time were fairly simple things. A barrel of some sort with two holes. One at the front for the projectile to come out. One in the back to light the powder that sent the projectile out.
Starting from there, people would go on to add different kinds of trigger mechanisms. Matchlocks which actually used a piece of burning cord to light the fuse. Flintlocks which used sparks to light the fuse. Percussion caps and the modern trigger mechanisms of today. All showed an evolution but didn’t do much to help the main issue that a smoothbore firearm had. Range and accuracy. You could aim at a target but hitting anything more than a couple of dozen yards away was a matter of luck more than skill. This was why armies stood in long lines real close together and firing all at once became the way wars were fought. The more muskets pointed in a direction, the better the odds were one would hit a target.
That all changed with the invention of rifling. Rifling, which is adding a series of groove to the barrel of a firearm, was first done in what would be Germany in the late 15th, early 16th century tough it would not become standard until the nineteenth century. The grooves in the barrel cause the projectile to spin which greatly stabilizes the flight due to centrifugal force. With its flight more steady the projectile more often than not would go to where it was aimed greatly increasing accuracy. Suddenly a bunch of men standing in line a few yards from each other became less of a good idea. Unfortunately, it would take a bit for tactics to catch up with technology and a lot of people dies needlessly. That is a story for another time though.
The pic above shows the rifling grooves on a Civil War-era cannon, looking down the barrel you could see the spiral pattern that imparted the spin which gave the guns the greater range and accuracy.