Patent GB-578583-A (GB)
Title: Improvements in riflings for ordnance
IPC: F42B30/10
Filed: 1939-07-28
Abstract: 578,583. Ordnance ; projectiles. SOC. HOLDING GENERALE DE BREVETS SOBRE. July.28, 1939, No. 21934. Convention date, July 30, 1938. [Classes 9 (i), 92 (i) and 92 (ii)] A dual-purpose gun 1 capable of firing either long-range projectiles stabilised by gyratory motion due to rifling, or short-range projectiles stabilised by fins, is characterised by the provision of rifling grooves 11, Fig. 8, having a depth between .05 and 2 mm. and closely spaced round the circumference, the number of grooves being greater than one half the number of millimetres in the circumference of the inner face of the lands. The grooves cooperate with a movable driving band 24, Fig. 6, giving gyratory motion to the long-range projectile and also serve, in conjunction with a gas check ring 59, Fig. 5, to reduce gas leakage when the short-range, projectile is fired. For a gun of 100 mm. calibre, the number of grooves will be of the order of several hundred and will resemble ratchet teeth. The rifling may be formed in the bore of the barrel of a Stokes' mortar mounted in the known manner on a base-plate and two-legged wheeled front support connected to the gun through a recoil spring (Fig. 1, not shown). The mortar is adapted to fire projectiles having driving bands and gas check rings as described in Specification 578,616. The mortar may fire a known finned projectile, Fig. 5, comprising a curved front followed by a gas check ring 59 in a groove 58 and a long tapered rear part 54 fitted with a perforated socket 55 containing a propellent charge and surrounded by additional propellent charges 57 in front of guiding fins 56. The same mortar may also fire a projectile, Fig. 6, stabilised by gyratory motion. The projectile has a long concavo-convex front part 12 and a shorter tapering rear part 13 fitted with a propellent tail-piece 14, but no guiding fins. The gas check ring is then replaced by a driving band device, for example, a split ring 24, Fig. 7, normally in a groove 23, but adapted when the shot is fired to be forced by the gun gases up into a serrated groove 25 and into the rifling 11. The action is assisted by an incline 38 on the gun. The ring 24 is ejected by centrifugal force on leaving the gun. The Specification as open to inspection under Sect. 91 also describes (1) with reference to Fig. 23 (Cancelled) a form of propellent tailpiece which comprises a perforated tube 14 secured to the projectile by a shear pin 16 and containing a punch 19, 20 in front of the propellent charge to shear the pin 16 when the shot is fired to detach the tail-piece from the projectile. External shoulders are formed by groovings 22 around the tail-piece to ensure its ejection from the gun : (2) with reference to Fig. 24 (Cancelled), a Stokes' mortar having a rifled tube 60 adapted to be inserted in the barrel 61 and to be secured therein by a bayonet joint 65 and a tightening screw 66. The tube 60 may be open at the rear end or closed as shown and fitted with its own firing- pin 68; (3) many forms of single and multiple driving band arrangements. This subjectmatter does not appear in the Specification as accepted.