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Conventional eight groove rifling on the left, and octagonal polygonal rifling on the right. Polygonal rifling (/ p ə ˈ l ɪ ɡ ə n əl / pə-LIG-ə-nəl) is a type of gun barrel rifling where the traditional sharp-edged "lands and grooves" are replaced by less pronounced "hills and valleys", so the barrel bore has a polygonal (usually hexagonal or octagonal) cross-sectional profile.
The gun used polygonal rifling, a principle invented by Whitworth in 1853.The concept was to use the hexagon to impart a very rapid spin to the projectile. The method of manufacturing the rifling was thus described by the Report of the Armstrong & Whitworth Committee of the British War Office (1866):
Rifling of a 105 mm Royal Ordnance L7 tank gun Conventional rifling of a 90 mm M75 cannon (production year 1891, Austria-Hungary) Rifling in a GAU-8 autocannon. Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy ...
The 100-ton gun (also known as the Armstrong 100-ton gun) [6] was a British coastal defense gun and is the world's largest black powder cannon. It was a 17.72-inch (450 mm) rifled muzzle-loading (RML) gun made by Elswick Ordnance Company , the armaments division of the British manufacturing company Armstrong Whitworth , owned by William Armstrong .
Whitworth had experimented with cannons using polygonal rifling instead of traditional rifled barrels, which was patented in 1854. The hexagonal polygonal rifling meant that the projectile did not have to bite into grooves as was done with conventional rifling. In 1856, that concept was demonstrated in a series of experiments using brass howitzers.
The HK P9 is a semi-automatic pistol from Heckler & Koch in 9×19mm Parabellum, .45 ACP, and 7.65×21mm Parabellum and the first to use a variation of H&K's roller delayed blowback system in a pistol format and polygonal rifling [1] now common in H&K designs.
Another feature of this pistol is the use of polygonal rifling in the barrel bore. This replaces the traditional lands and grooves rifling design with a rounded, smooth polygonal pattern which has a more "hills and valleys" appearance. The CZ 83 was set to discontinued/limited production status by CZ USA in 2012. [1]
The machine gun's weight was increased, a carrying handle and a hooked buttstock with improved buffer mechanism were also added. [6] The barrels were internally revised to polygonal rifling . Since then, the HK21 was offered in two main variants: the HK21A1 general-purpose machine gun (with a different belt feed mechanism) and the HK11A1 light ...