Taylor knock-out factor The Taylor knock-out factor (TKOF) was developed as a measure of stopping power for hunting game, however it is a rather flawed calculation. It is defined as the product of bullet mass, velocity and diameter, using the imperial units grains (equal to 64.79891 mg), feet per second (equal to 0.3048 m/s) and inches (equal to 25.4 mm): Some TKOF example values for shotgun slugs are: 71 TKOF for a 70 mm (2 3/4 in) slug (i.e. 437.5 grain (1 oz) × 1,560 FPS × 0.729 caliber /7000 = 71.07 TKOF) 80 TKOF for a 76 mm (3.00 in) slug (i.e. 437.5 grain (1 oz) × 1,760 FPS × 0.729 caliber /7000 = 80.19 TKOF) To compare with rifles, some TKOF example values for rifle cartridges are: Types Full-bore slugs Full-bore slugs, such as the Brenneke and Foster types, contrary to popular belief, use a spin-stabilization method of stabilization through the use of angled fins on the slugs outer walls. The slight 750 RPM spin is enough to stabilize the slug because the slugs center of pressure is so much further back than its center of mass. Saboted slugs are similar in shape to handgun bullets and airguns slugs. Their center of pressure is in front of their center of mass, meaning a higher twist rate is required to achieve proper stabilization. Most saboted slugs are designed for rifled shotgun barrels and are stabilized through gyroscopic forces from their spin. Brenneke slugs The Brenneke slug was developed by the German gun and ammunition designer Wilhelm Brenneke (1865–1951) in 1898. The original Brenneke slug is a solid lead slug with ribs cast onto the outside, much like a rifled Foster slug. There is a plastic, felt or cellulose fiber wad attached to the base that remains attached after firing. This wad serves as a gas seal, preventing the gasses from going around the projectile. The lead "ribs" that are used for inducing spin also swage through any choked bore from improved cylinder to full. The soft metal, typically lead, fins squish or swage through the choke to allow for an easy passage. Foster slugs The "Foster slug", invented by Karl M. Foster in 1931, and patented in 1947 (), is a type of shotgun slug designed to be fired through a smoothbore shotgun barrel, even though it commonly labeled as a "rifled" slug. A rifled slug is for smooth