In today's increasingly competitive business environment, managing software engineering projects has become more challenging and complex. Project managers are expected to deliver high quality products in a shorter time with fewer or less expensive resources. Despite the availability of well-established project management frameworks and innovative tools and techniques, software projects still fall short of meeting their time, cost and quality objectives. While there are many studies that treat projects as 'black boxes' and retrospectively analyse the externally apparent characteristics of projects that might influence their success, this work addresses the internal processes of project management. This paper describes the methods developed to conduct an empirical study into the internal dynamics - often reacting to external events - of software project management during project execution focussing on the Design, Build, and Test (DBT) stages of the application development lifecycle. The data used comes from a case study carried out at a large software development company which uses an incremental delivery model with intensive parallel development in a multi-location team environment. The main research concerns of the overall study are the extent to which the project performance indicators currently used provide enough information to project managers to make good decisions, and the range of issues that occur during project execution that affect the project's ability to achieve its time, cost and quality objectives. This paper discusses the research methods that were eventually adopted. The original intention was to build numerical models using the largely quantitative data generated by the project management processes. The study now employs a mixed methods approach using a 'convergent parallel' model (Creswell & Clark 2011). Quantitative and qualitative data are collected in parallel, analysed separately, and then merged for interpretation. This approach provides a more complete understanding of the project management processes and issues. A Grounded Theory approach was used to analyse the textual progress reports generated on a weekly basis during the execution of the project. As well as giving insights into the obstacles to progress experienced, this also provided a view of how the progress reports were used by individuals to influence perceptions of the individual elements of the project. This paper focuses on the research approach adopted in the study and its suitability for use in empirical software project management research. The study findings demonstrate that considerable benefit can be gained from using mixed methods approach to obtain a fuller understanding of the management dynamics of project execution.