A new technique has been devised to examine deformation microstructures of thin walled metal cylinders subjected to internal impulsive loading. The cylinders are strained finite amounts but are not carried to fracture. The stressing device uses a rigid stainless steel cell as a container and an explosively driven Lucite core to produce specimens of metals and alloys that have undergone a high strain rate expansion and are in a form amenable to direct observation by transmission electron microscopy. The total strain in the specimen is controlled and loading conditions may be reproduced for comparison of different materials. This approach is particularly well suited to the detailed investigation of explosive forming processes and shock hardening phenomena in cylindrical bodies.