The Effect of Ribbing and Boat-Tail Length on a Bullet’s Drag

From Minié balls during the Civil War to incendiary rounds in the present, the world of ballistics has made great improvements in the realm of bullet designs. Now that guns are so powerful, bullet specialists are faced with the challenge of minimizing drag to maximize the bullet’s range. Less drag means target shooters, hunters, and soldiers can hit objects from farther away giving them an edge in their respective fields. Drag is determined by multiple factors but primarily on the shape of the bullet such as indentations on the surface and the length of the bullet. Thus, bullets with ribs and boat-tails were tested to find the one with the least drag. The results of this experiment can be applied to future bullet designs to minimize drag and make bullets fly farther.

In this experiment, nine bullets with different ribbing combinations (0, 3, 5 ribs) and boat-tail length (0, 1.5, 3 inches) were created and evaluated in a wind tunnel. The drag for each bullet was then calculated from the force measured by a force sensor. The results were analyzed using visual analysis, an ANOVA, and three two-sample t-tests. The ANOVA proved that the variations in designs did have an effect on the drag of the bullets and by visually inspecting the data, it was clear that the drag decreased as the boat-tail length increased. Also, the bullets with three ribs were significantly better than those with either zero or five ribs. The bullet with the least drag was the one with a full boat-tail (3 inches) and three ribs. Furthermore, the bullet with the most drag had no boat-tail and five ribs, though the bullets with five ribs were generally better than those with zero ribs.

Research Conducted By:

Ryan Caliguri
Warren Mott High School

Jeffrey Wainz
Warren Mott High School