Abstract: A test fixture is provided for evaluating structural response of a sample to blast pressure from a muzzle of a gas gun. The fixture includes an adapter, an annular flange, a gauge assembly and a target assembly. The adapter has a proximal rim and an expansion tube. The rim attaches to the muzzle to direct the blast pressure into the tube towards an exit opposite the rim. The annular flange has a ring and a shim that attaches to the tube at the exit. The gauge assembly contains the sample between upstream and downstream stress gauges. The target assembly contains the gauge assembly. The target assembly includes front and rear annular plates connecting coaxially in parallel. The rear annular plate connects to the ring. The tube carries the blast pressure through the exit to strike the gauge assembly for the stress gauges to measure stress from the blast pressure.