The Influence of Additives on the Temperature, Heat Transfer, Wear, Fatigue Life, and Self Ignition Characteristics of a 155 mm Gun

The temperature and heat transfer per round was measured at the bore surface of a 155 mm AS90 extended range ordnance. The ammunition was fired with and without wear-reducing additive and the measurements were made using an eroding-type surface thermocouple having response time of about a microsecond. The heat transfer was computed from the measured temperature-time curves. It was found that the wear-reducing additive gradually reduced the surface temperature fluctuation from about 950°C to about 600°C, and reduced heat transfer per round from about 950 kJ/m² to about 600 kJ/m², over a period of 50 rounds. From these measurements an assessment was made of the wear rate, the number of rounds to cook-off, and the increase in barrel fatigue life. Similar experiments on 30 mm RARDEN and 40 mm Bofors guns, using different additives, resulted in comparable reductions in bore temperature and heat transfer, but the mechanism for these reductions was different and it is still not clear exactly how these additives reduce barrel temperature and heat transfer.