Indian Head Division. Naval Surface Warfare Center. Indian Head. 1996. – 11 p.Firing records covering the master powder shots associated with over 15 years worth of 5-in powder proof firings are examined for velocity degradation over time. None is found, though an increase in velocity is seen. An explanation for this behavior is offered.
The approach used was to examine the records from powder proof firings over as long a period as the same master powder was in use. Data for master powder shots for each lot fired were compiled and compared to ascertain whether any loss in velocity was noted. Only 5-in propellant (Naco) was studied since there have been only 17 lots of M6+2 made and proofed for the 76-mm system and this seemed too small a sample to develop reliable trends. The velocities for all the shots for a given barrel (Remember that four barrels are used for proofing 5-in powder.) were plotted against the age of the powder as measured from the powder's proofing, then a line was fit to the data as shown in Figures 1 through
4. In all four cases, the velocity rose over time, though the degree varied by barrel. The initial velocity for each gun barrel (which had seen proof firings only) also varied.
Over a twenty year period, master powder index 11041 has shown an increase in achieved velocity, averaged over four gun barrels, of approximately 20 ft/s. With the process of lapping to explain the increase in velocity which the rounds exhibited over a number of years, we can be comfortable in stating that the performance of loaded rounds is not expected to change appreciably over time and that no correction need be applied in the fire control solution for older rounds. This assumes that propelling charges have been stored properly throughout their lifetimes (in accordance with 0P4 and 0P5), having experienced no unacceptable storage environment excursions.Contents:
Foreword.
Introduction.
Approach.
Discussion.
Conclusion.
