Why did early smoothbore muskets have poor accuracy?

Early smoothbore muskets suffered from poor accuracy primarily due to the necessary clearance between the projectile and the barrel, a space known as windage.12

To allow for rapid reloading via the muzzle, the lead ball had to be smaller than the diameter of the bore so it could be easily rammed down to the breech. When the musket was fired, this loose fit caused the ball to wobble as it traveled down the barrel, resulting in an erratic flight path once it exited the muzzle.1

While rifled barrels were known to improve accuracy by imparting a gyroscopic spin to the projectile, they were not widely adopted for standard infantry use for a long time because the tight fit required for the rifling significantly slowed the rate of fire compared to smoothbore muskets. Consequently, infantrymen relied on volley fire to compensate for the inherent ballistic limitations of their smoothbore weapons.1