"T" Friction tube, special Push version, Mk I, for British BLC 15 pounder gun.
Introduced to enable the gunlayer to fire the gun in similar manner to a Q.F. gun, without needing to hook a lanyard to the tube for firing :-

• The tube was inserted into an axial vent in the breech.
• The breech mechanism incorporated a firing plunger to push the friction bar in the tube.
• When loaded, the gunlayer activated a firing handle on the layer's guard behind and on the left side of the breech. This activated a firing lever above the breech, which in turn activated the firing plunger below it.
• When pushed, the friction bar shears the suspending wire, travels forward, the roughened conical part of the bar pierces and fires the detonator.
• The push bar also carries portions of the composition and grinds it against roughened interior of the head, further ensuring ignition.
• The flash passes down through the plug in the body, fires the powder in the tube, sending a flash along the radial vent in the "mushroom" and into the chamber and and hence fires the cordite charge.
• The copper ball is driven upwards by the explosion and seals the head against escape of gas.
• From 1909 a small escape hole was added to the head to allow gas from exploding cap to escape, and hence prevent the head expanding and jamming in the vent.