Tamisier

Ball grooves

Captain Tamisier obtained a patent in 1841 for a method to improve the accuracy of cylindro-conical shot, by cutting three sharp grooves (French: "cannelures") on the cylindrical part of the shot.

Compared to round shots, which offered a rather inefficient but symmetrical and stable aerodynamic round profile, the aerodynamic stability of the cylindro-conical shot had been an issue in early rifled weapons of the type developed by Delvigne. Through Tamisier's method, the resistance of the air behind the center of gravity of the shot was increased, thereby increasing its stability, in a manner similar to that of arrow feathers in an arrow (fletching), or shuttlecocks. The shot would thus remain stable in flight and increase greatly in efficiency. Tamisier had experimented with the ball developed by Delvigne to discover the effect of aerodynamic resistance on the trajectory of a bullet. The cannelures served more to carry black powder fouling out of the rifling. The effect of "base drag" served more to stabilize along with the rotation of the rifling to make the bullet more accurate than a round ball. At near the speed of sound feathery projections serve little purpose. the suggestion that they may behave like a sporting tool of a badminton toy is inept and asinine and totally without physical evidence or science. Base drag along with rifling rotation stabilized Minnie Balls. After the nose of the bullet penetrates the atmosphere the shock wave created by the impact with gas molecules of air creates pressure, friction and drag. A vacuum forms in the wake of the line of flight of the bullet. This exertion on the rear end of the projectile tends to pull the entire bullet in a varying gyration that is caused the rotation. The minie spins around its center of mass and in traveling against air is caused to wobble against varying pressure laterally due to vacuum on the base of the bullet. In this case it is a hollow skirt of lead. The point always hits first. this has nothing at all to do with Archery. Bill G. says this is fantasy and a misconception of how it actually works.

The Tamisier grooves greatly improved the efficiency of the cylindro-conical bullet. However they rendered the forcing of the bullet against the grooves of the rifle bore in the Delvigne system rather difficult. To accommodate this difficulty, the stem rifle was developed by Thouvenin. These principles were later incorporated in the design of the Minié ball.

Progressive rifle grooves

Tamisier also developed a method for making rifle grooves, which was original in that the grooves were deeper at the breech and progressively shallower towards the muzzle. This provided for a progressive forcing of the ball as it moved through the barrel, greatly improving its efficiency.