U.S. Naval proving ground. 1954.A rapid fire life test has been conducted in 3''/70 caliber gun Type C Mod 2 Serial No. 24483 employing a cool double base picrite propellant# The results of this test were reported in reference. The Bureau of Ordnance has directed that a similar test in a similar barrel employing a cool single base non-picrite propellant be conducted in order to establish the relative erosion rate for the two propellants. 3”/70 Caliber gun Type C Mod 2 Serial No. 24583 was used in this latter test.
The planned firing program consisted of five 15-round bursts with five second interval between bursts. The rate of fire was to be 90 rounds per minute. Barrel No. 245B3 was fired a total of 957 rounds. At that time asymmetric forward bore wear had developed to such an extent that further firing was not deemed advisable.
The wear rate near the origin of bore with cool non-picrite powder closely approximates that with cool picrite powder. The forward bore wear in barrel No. 24563 (fired with cool non-picrite powder) was much more severe than in barrel No. 24483 (fired with cool picrite powder). The cause of the disparity in forward bore wear cannot be resolved at this time. Conceivably the propellant composition could be a contributing factor. Metallurgically one barrel may differ from another sufficiently to cause considerable variations in barrel wear. In both barrels forward bore wear was more severe than has been experienced in the 3’’/70 Caliber Gun Type G Mod 7 under single fire conditions.
