High-pressure research is one of the fastest-growing areas of natural science. The European Commission is funding the Sample Environment Joint Research Activity (JRA) between major European neutron scattering facilities within the NMI3 FP7 framework. In this collaboration ISIS is responsible for the high pressure gas vessel development project. The main aim of the project is to raise the upper limit of the vessel operating pressure while keeping to a minimum the thickness of material in the neutron beam. To achieve this ambitious aim we need to push design and material boundaries, while still knowing the vessel is safe. Autofrettaging is a key technology used to produce usable high pressure vessels. Finite element analysis (FEA) and empirical formulae can be employed to estimate the position of the plastic/elastic transition in a vessel wall which has undergone autofrettag