What is the purpose of having lands and grooves inside the barrel of a rifle?

The purpose of having lands and grooves inside the barrel of a rifle is to impart a spin to the bullet as it is fired. This spin stabilizes the bullet in flight, which significantly enhances its accuracy and improves its trajectory. The rifling, characterized by the alternating raised (lands) and recessed (grooves) portions, grips the bullet and causes it to rotate around its axis. This rotation helps to maintain a straighter path through the air, thus reducing the effects of wind and other environmental factors that could affect accuracy.

In contrast to other choices, the weight of the bullet is unaffected by the rifling, and while some designs may help manage recoil, that is not the primary function of lands and grooves. Additionally, while aesthetics can play a role in firearm design, the primary purpose of rifling is functional, aimed at improving shooting precision.