User:MightDo/sandbox/Woolwich Rifling System

The Woolwich System was one of the technologies used to create axial projectile rotation in early British rifled muzzle-loading ("RML") guns. It was exclusively used in the first generation of heavy guns and howitzers (calibres 7 inches to 12.5 inches introduced before 1878) and was also used in the 40 pr and 25 pr guns.

Axial Projectile Rotation
Axial projectile rotation ("rotation") is necessary to maintain projectile stability during flight. Without it, projectiles would tend to wobble or tumble, reducing range and accuracy, and potentially failing to deliver the projectile to the target point first. Rotation is produced by cutting a number of parallel spiral grooves ("rifling") along the inside surface of the barrel, and making the surface of the projectile engage with these grooves in some way so that rotation is imparted to the projectile as it travels along the barrel during firing.

Woolwich System
In the Woolwich system, the grooves had particular geometrical characteristics and were called "Woolwich grooves". While the exact dimensions of the grooves varied between guns of different sizes, their overall geometry was similar. Woolwich were initially "studded" i.e. there were rows of soft metal studs along the sides of each projectile. The studs slid along the grooves during firing, forcing rotation of the projectile. The number of grooves varied with the size of the gun. The 25 pr gun had 3 grooves, while the 12.5 inch gun had 9 grooves.