boattail

A boattail is a tapered rear end applied to certain projectiles and aerodynamic bodies, most notably bullets and artillery shells. The term derives from the resemblance of the tapered base to a boat hull’s stern. Boattails are used to reduce aerodynamic drag and improve stability at high speeds, contributing to better ballistic performance in long-range applications. The concept extends to other streamlined shapes, including missiles, rockets, and some high-speed aircraft components, wherever base drag is a concern.

In ammunition design, a boattail base narrows toward the rear of the bullet, transitioning from the main body to a smaller-diameter base. This reduction in base drag decreases the wake behind the projectile, increasing the ballistic coefficient and enabling better velocity retention and flatter trajectories, especially at extended ranges. Boattail bullets are often contrasted with flat-base designs; the choice involves trade-offs, including manufacturing complexity and feeding considerations for certain firearms.

Beyond bullets, boattail configurations are used on missiles and rockets to minimize base drag and improve overall aerodynamic efficiency at supersonic or hypersonic speeds. The underlying principle is to shape the rear of a body to mitigate turbulent flow and pressure drag, thereby enhancing range and performance.