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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.
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.
A female worker boring out the barrel of a Lee-Enfield rifle during WWI. Gun barrels are usually made of some type of metal or metal alloy.However, during the late Tang dynasty, Chinese inventors discovered gunpowder, and used bamboo, which has a strong, naturally tubular stalk and is cheaper to obtain and process, as the first barrels in gunpowder projectile weapons such as fire lances. [2]
The ACR "rifles" used smoothbore barrels to fire single or multiple flechettes (tiny darts), rather than bullets, per pull of the trigger, to provide long range, flat trajectory, and armor-piercing abilities. Just like kinetic-energy tank rounds, flechettes are too long and thin to be stabilized by rifling and perform best from a smoothbore barrel.
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 barrel and mandrel are rotated and hammered by power hammers, which forms the inside of the barrel. This is the fastest and often cheapest method of making a barrel, but the equipment is expensive. Hammer-forged barrels are generally not capable of the accuracy attainable with the first two methods mentioned.
The hot air in conventional ovens just hangs around and sometimes leads to uneven results. Cooking With Convection Since convection ovens work so fast, the foods don't have to be cooked for as ...
The rifle can also mount a 40mm under-barrel grenade launcher. [3] It has a magazine capacity of 30 rounds. The cyclic rate of fire is 680 rounds per minute, and the sustained rate of fire is 120 rounds/min. [3] The Zastava M21 uses a conventional barrel, while the Zastava M21B uses a polygonal barrel. The regular barrel has six grooves with a ...