Honeycomb sandwich structures have widespread use in structural engineering. They provide a strong and efficient method for reacting structural loads. The design of these structures requires that the facesheets react in-plane and bending loads and the core react the transverse shear load. Knowledge of the material properties of the core is required, and several test methods are available to the design engineer to develop these properties. ASTM C393 determines core shear properties by the flexure of a simply supported beam, while ASTM C273 generates core shear properties by bonded loading plates loaded in either tension or compression. ASTM C273 is preferred method for generating core shear strength and shear modulus. Two loading options are given in this test protocol. One specifies loading the specimen in tension and the second specifies compression loading. The ASTM protocol notes that “the test does not produce pure shear, but the specimen length is prescribed so that secondary stresses have a minimum effect”. Testing and analysis are performed to determine the effectiveness of the test procedure. Issues are identified in this paper with the shear modulus measured. A recommendation is made for a minor modification to the ASTM C273 test protocol to address the issues described.