"David" high-velocity anti-tank gun

[Tony Williams]

A paragraph from Ian Hogg's "British and American Artillery of World War 2":

"An interesting derivative of the 2pdr was the Canadian "David" high-velocity gun. This was designed in 1942 and was essentially a 2pdr with an enlarged chamber and a 6pdr breech firing a round which comprised a 2pdr shot and a 6pdr cartridge case. Development was slow, because of problems in ammunition design. A gun and ammunition were sent to Britain for trials, but there were still in progress when the war ended. The project was finally abandoned, but it had yielded much useful information on high-velocity guns which proved useful in other applications".

You can see photos of the ammunition here.
The cartridge case is significantly wider and longer than that of the 40mm Bofors, which itself was slightly bigger than the cartridge for the British 2 pdr tank/anti-tank gun.

Does anyone know of a source of information or photos of this gun?