In 1977 and 1978, Bull orchestrated the illegal sale of 30,000 155mm artillery shells, gun barrels and plans for the GC-45 howitzer as well as radar equipment to Armscor, the South African state arms corporation; with two shipments made through Antigua in 1978 and another through Spain in 1979. The South African Defence Force's arsenal of vintage howitzers – antiquated by the arms embargo – had been outperformed by BM-21 Grads during "Operation Savannah" in 1975. In order to counter the modern Soviet artillery deployed in neighbouring Angola, South African officials began seeking longer-ranged weapons systems and were referred to SRC. Armscor trialled the GC-45 with a new mounting to allow for increased powder loads and installed an auxiliary power unit for improving mobility in the field. The resulting G5 howitzer was vital to South African campaigns against Cuban expeditionary forces in Angola, allowing them to target infrastructure and personnel with phenomenal accuracy. In addition, the urgent shipments were also meant to address the acute shortage of artillery shells due to their incursion into Angola.