SELF ADJUSTING OBTURATOR

The performance of guided projectiles fired in smooth-bore Navy guns is progressively degraded by barrel wear: once high temperature propellant gasses start to flow (jet) between the wall of the gun barrel and the body of the projectile, barrel wear is accelerated and propellant efficiency drops off progressibvely degrading gun accuracy. Advanced Technology and Research Corporation (ATR) proposes that the research and experimental work conducted jountly by Codes EPA and 702 of NSWC (1974) on nonmetallic 5"/54 gun projectile rotating bands be reinstated to evaluate the same materials for use as obturators for smooth-bore, 5-inch guided projectiles. Mr. DeVost of ATR was the NSWC/WL senior engineer assigned to the EPA rotating band program. ATR will conduct research jon related information obrained in the mid-1970s by Codes EPA and EPM. Also, information will be researched on modern plastics. After a selection is made of candidate obturator materials, samples will be fabricated and tested for closure plug impact, setback shock and obturator integrity. Shock tests will be conducted on the ATR, mega g Mechanical Shock Sensor Test Apparatus. Scale-model studies on obturators will be conducted in a shot gun: obturators will be fired behind standard shot gun slugs in new and simulated-worn barrels; blowby pressures will be monitored at muzzle break.