Ballistic shelf life of propellants for medium and small calibre ammunition - influence of deterrent diffusion and nitrocellulose degradation

(Фогельсенгер Бит, Oссола Бруно, Шедели Ульрих, Aнтенеон Доминик, Рyф Курт. Баллистический срок годности порохов для боеприпасов среднего и малого калибра - влияние средств сдерживания диффузных процессов и деградации нитроцеллюлозы). — Interlaken, Switzerland: 19th International Symposium of Ballistics. 2001. – 8 p.The reasons for ageing-induced changes in interior ballistic behaviour of small and medium calibre ammunition have been investigated. In case of the 5.56 NATO ammunition, two different propellants have been subjected to accelerated ageing at 71°C for 4 weeks. The ammunition filled with ball powder showed an ageing-induced increase in peak pressure of 75 MPa, whereas ageing of the ammunition with the alternative EI propellant (EI = extruded impregnated) did not result in a peak pressure rise. Diffusion could be identified to be a dominating factor. Further results are presented, proving that the ageing-induced changes in interior ballistic behaviour of surface coated medium calibre propellants directly correlate with the extent of deterrent diffusion. In certain propellants, deterrent diffusion is so fast that it can be monitored even at room temperature. On the other hand, excellent ballistic shelf life can be obtained if surface coatings with low diffusion potential are applied.