The report describes modelling and instrumented experiments for studying thermal initiation of nitrocellulose-based propellant used in rifle ammunition of calibre 12.7 mm. The study is motivated by the benefits of knowing the risks for self-ignition during ammunition storage, and by extension suggest reliable and cost-effective methods for ammunition surveillance. Three different experiments are modelled, namely "Accelerating Rate Calorimetry" (ARC), "Instrumented Cook-Off Test" (ICOT) and slow heating tests on full cartridges. The model considers transport of heat in the propellant and the container coupled with chemical kinetics of propellant decomposition. For the kinetics, two models are evaluated, where one describes the decomposition with a single step and the other accounts for an elementary autocatalytic effect. The one-step model is shown to be inadequate to describe the three experiments. The autocatalytic model, calibrated against the ICOT tests, is however shown to describe the ARC and slow heating tests well. The results constitute a valuable basis for selecting experiments and modelling strategies in the continuing study of propellant sensitivity during long-term storage.