Strain Gage Measurements, 3in/70 and 5in/54 Guns

The maximum and radial strains on the breech face of 3-in.70-cal and 5-in.54-cal guns were measured by wire resistance strain gages located on the breech face near the outside diameter. HKPC-1 powder was used with Mk 10 cases and Ex-24 Mod 2 projectiles in the 3-in.70-cal gun which was fired in a 5-in. 38-cal mount with a Mk 24 Mod 5 slide IHBF-3 powder was used with Mk 7 cases and Mk 41 Mod 0 70-lb projectiles in the firings in a Mk 28 Mod 2 slide of the 5-in.54-cal type-G Mod 0 gun. The maximum tangential breech face strain recorded for the 3-in.70-cal gun was 740 micro in.in., with a charge weight of 10.50 lb and a Cu crusher pressure of 23.4 TSI. For the 5-in.54-cal gun, the maximum strain was 895 micro in.in., with a charge weight of 21.4 lbs., and a Cu crusher pressure of 25.7 TSI. The tangential strains on both guns were slightly greater on the right of the center line. These differences were attributed to the unsymmetrical structure of the slide and housing, and the unsymmetrical location of the interrupted threads in the housing with respect to the gages.