While they waited for the guns to be fabricated by the Naval Gun Factory, various propellants were tested. Hirschfelder sent John L. Magee to the Bureau of Mines' Experimental Mine at Bruceton, Pennsylvania to test the propellant and ignition system. Test firing was conducted at the Anchor Ranch with a /50 caliber gun. This allowed the fine-tuning of the testing instrumentation. The first two tubes arrived at Los Alamos on 10 March 1944, and test firing began at the Anchor Ranch under the direction of Thomas H. Olmstead, who had experience in such work at the Naval Proving Ground in Dahlgren, Virginia. The primers were tested and found to work at pressures up to . Brode's group investigated the fusing systems, testing radar altimeters, proximity fuses and barometric altimeter fuses.
