the L17 carriage. The L19 ordnance is slightly shorter than the L13 used by the Abbot and hence has a slightly shorter maximum range. Also, unlike the Abbot, the barrel is autofrettaged and hence lighter. The light gun appears to owe a number of its features to the QF 25 pounder, unsurprisingly since RARDE was the successor to the design department, Woolwich Arsenal. Among these features are its vertically sliding block breech, and a box trail instead of a split trail; a traversing platform is normally used with it. Its comparatively light weight is also attributed to the nature of the steel used in the carriage and ordnance, and other weight-reducing features, including its narrow wheelbase. The narrow wheelbase prevents the ordnance rotating the 3200 mil (180°) required to 'unfold' the gun. Because of this, the gun features a knock-off hub on one side allowing the ordnance to be rotated by removing one wheel. With a well trained gun crew, this contributes approximately 30 seconds to the time required to deploy the gun. In British service, rotating the barrel for towing is optional. When being towed in the unfolded position, the A-frame is fitted to the front transom in order to support the elevating mass. A recent modification makes it possible to keep the gun in this position indefinitely at speeds up to . For long distance transport or traversing rough terrain, the barrel is reversed and clamped to the end of the trail. For storage, the gun is in the unfolded position with the barrel elevated to an angle that balances the elevated mass on the yoke and therefore relieves pressure on the elevating gears. When first introduced in the British Royal Artillery, the L7 or L7A1 dial sight and its carrier, incorporating an integral elevation scale and internal lighting powered by Trilux nuclear light sources, was used to aim the gun for indirect fire. The L7 sight is a modified version of a German Leitz instrument. Since the light gun entered service after the introduction of field artillery computer equipment (FACE), it never, unlike the Abbot, had gun rules (large slide rule like instruments used at each gun to convert range in metres to tangent elevation in mils, taking account of muzzle velocity). Therefore, it has a single quadrant elevation scale. These optical indirect fire sights are now only used in recruit training. The guns also have a