What is the purpose of rifling in the M4?

Rifling in the M4, which consists of helical grooves cut into the barrel, serves the primary purpose of improving accuracy. The design of rifling creates a spin on the bullet as it exits the barrel. This spin stabilizes the projectile in flight, allowing it to maintain a straighter trajectory over longer distances. As a result, the bullet is less susceptible to external factors such as wind, which enhances precision and groupings when aiming at targets.

While increasing speed could be a secondary effect related to the overall design of the barrel and ammunition, the primary function of rifling is specifically aimed at accuracy. The other factors mentioned, such as reducing recoil and enhancing durability, do not directly correlate with the role of rifling in altering how a bullet behaves once fired. Thus, the improvement of accuracy through the stabilization of the bullet is why this aspect of rifling is critical to the functionality of the M4.