A HIGH-PERFORMANCE AUTOMATIC AIRCRAFT CANNON BARREL.
ARMY WEAPONS COMMAND ROCK ISLAND ILL RESEARCH AND ENGINEERING DIRECTORATE
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Design parameters and materials are described to obtain an optimum barrel design for the 30mm XM140 Automatic Aircraft Cannon. The optimum design was based on the actual dynamic properties of the barrel material at elevated temperatures. Barrel temperatures on the outside diameter approaching 2000 degrees F during long bursts made conventional design practice unusable. Stresses at elevated temperatures approach the dynamic yield point. Wall ratios down to 1.25 near the muzzle were required to meet space and weight limitations. Comparative data taken during the actual firing tests are shown for an iron-nickel base alloy, a chromium-molybdenum-vanadium low-alloy gun steel and a typical nonferrous superalloy. A metallurgical method is described for the determination of the actual maximum barrel temperatures within 50 degrees F. Effects on the bore of superalloy barrels after continuous bursts of 400 to 600 rounds are shown in photographs. Author