The Small Arms System Agency at Aberdeen Proving Ground sponsored a research project in December 1969 for the development of a 5.56mm expendable or expellable case design. Most of this development was done by Remington and the project was aimed at solving the combustible case vulnerability problem b enclosing the propellant in a rimless, grooveless plastic body which was expelled through the muzzle when fired. The concept was called “XC” for expellable case and consisted of a special chamber with free space at the base and neck, so that it allowed the case to collapse, break up and is expelled from the test barrel. Various designs were tested and the specimen below is called Design 7C which was loaded with a standard M193 bullet.

             shown at 200% scale

Another version loaded by Remington in 1972 has a black plastic case and was also loaded with the M193 bullet.

           shown at 200% scale