page_title: Rifled breech loader
section_title: Quickfiring guns
hierarchical_section_title: Rifled breech loader / History / Quickfiring guns
caption_attribution_description: Closeup photograph showing coned interrupted thread breech of British QF 6 inch naval gun on cruiser HMS Ariadne.
context_page_description: A rifled breech loader is an artillery piece which, unlike the smoothbore cannon and rifled muzzle loader which preceded it, has rifling in the barrel and is loaded from the breech at the rear of the gun.
  The spin imparted by the gun's rifling gives projectiles directional stability and increased range. Loading from the rear of the gun leaves the crew less exposed to enemy fire, allows smaller gun emplacements or turrets, and allows a faster rate of fire.
context_section_description: The first quick-firing light gun was the 1-inch Nordenfelt gun, built in Britain from 1880. The gun was expressly designed to defend larger warships against the new small fast-moving torpedo boats in the late 1870s to the early 1880s and was an enlarged version of the successful rifle-calibre Nordenfelt hand-cranked "machine gun" designed by Helge Palmcrantz. The gun fired a solid steel bullet with hardened tip and brass jacket.
  It was superseded for anti-torpedo boat defence in the mid-1880s by the new generation of Hotchkiss and Nordenfelt "QF" guns of 47-mm and 57-mm calibre firing exploding "common pointed" shells weighing 3–6 pounds.
  The French firm Hotchkiss produced the QF 3 pounder as a light 47-mm naval gun from 1886. The gun was ideal for defending against small fast vessels such as torpedo boats and was immediately adopted by the RN as the "Ordnance QF 3 pounder Hotchkiss". It was built under licence by Elswick Ordnance Company.
  Both the Hotchkiss and Nordenfelt guns loaded ammunition as a single cartridge with projectile, cartridge case and primer in a single unit. The cartridge case sealed the breech on firing and a vertical sliding wedge (block) locked it in place. These new guns incorporated recoil control devices which facilitated consistency of aim, allowed single-motion loading and could be fired as soon as the cartridge was inserted, and then ejected it after firing, these properties denoting a "quick-firing" gun. This set a new standard for artillery, and made firing cycles measured in seconds rather than minutes possible.
  Britain used brass cartridge cases for all calibres up to 6 inches in the late 1880s and early 1890s. However, British-designed quickfiring ("QF" in British terminology, which became synonymous with charges in metal cartridge cases) continued to use screw breech blocks, but with their function merely to lock the cartridge in place rather than provide obturation. The powerful backward force generated by 6-inch QF guns still required a strongly seated breech screw with as much thread as possible. However, a basic interrupted-thread screw sufficiently long enough to have enough thread to secure the cartridge on firing still required three separate motions to operate – rotate, withdraw, swing aside after firing, and repeated in reverse before firing.
  Elswick Ordnance Company (Armstrong's ordnance arm) developed a coned version of the interrupted-thread screw, with a decreasing rather than constant diameter towards the front. This eliminated the second "withdrawal" motion, with just two motions now necessary, rotate and swing aside. This proved short-lived, with Britain adopting charges in bags using the Welin stepped interrupted screw for all guns 5 inches and up within several years of it becoming available.
caption: Elswick coned interrupted screw breech of QF 6-inch naval gun.
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