A boat-tail is also a particular shape used in the rear of a bullet. As bullet velocities increased with the advent of cartridges, high-pressure firearms, smokeless powder and the spitzer bullet tip it became evident that bullets were being heavily affected by drag. One of the first (and best, so far) modifications to the standard bullet design after the spitzer was the use of a tapered rear profile, called a 'boat-tail' for its resemblance to a watercraft's tapered stern.

As the bullet approaches transonic velocities, airflow which has been directed around the bullet by a sharp spitzer point meets the edges of a very low pressure area directly behind the bullet. If the airflow passes across the rear edge of the bullet moving parallel to the bullet's direction of flight, as it would if the rear had a flat cross-section, the low-pressure area is maximized and the interface turbulence contributes to the bullet's drag coefficient being higher. If, however, the sides of the bullet 'taper in,' the airflow is moving slightly 'inwards' and both minimizes the low pressure area and hence drag as well as minimizes the turbulent interface zone.

The boat-tail was first seen on a standard cartridge with the 1901 French Balle D bullet for the 8mm Lebel cartridge - the same bullet which first introduced the spitzer bullet to military standard ammo.

Boat"-tail` (?), n. Zool.

A large grackle or blackbird (Quiscalus major), found in the Southern United States.

 

© Webster 1913.

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