Mike, We made 3 inch mortars, Mills bombs, built bodies for trucks, built Beaverettes, built Carriers, (1060?), but until WWII we were at the teat of mother England (is it ok to say that?) We were suddenly weaned off under duress and a shortage of gauges and skilled gaugemakers was the first problem.
As with Australia, heavy industry was centered around the railways. I don't believe we produced any artillery. (I am the wrong person to answer this)
When I was a kid, my Dad talked about making a pelting machine for pelting rocks at the moon....
You obviously need a copy of Jeff Plowman's book "Armoured Fighting Vehicles of New Zealand 1939-59"