the weapon were as follows: It must weigh less than It must throw enough fragments so that at a range of it achieves a 100 percent strike rate on a target (man sized) The fragment area must not be more than high and no more than 60 degrees wide Fragments must have a velocity of per second providing 58 foot-pounds (79 joules) of kinetic energy delivered to the target. The requirement for kinetic energy was based on the fact that 58-foot pounds is required to deliver a potentially lethal injury. Given the requirements of weight and fragment density, approximately 700 fragments were needed, with the ability to aim the mine with an accuracy of around at the center of the target zone. The team at Aerojet were given access to all previous research into directional mines, including the M18 and the Phoenix, as well as German research. Dr. John Bledsoe led the initial project. The original M18 mine fell far short of Picatinny's requirements. One of the first improvements was to replace the steel cubes with hardened 52100 alloy ball bearings. These performed poorly for two reasons. Firstly, the hardened steel balls spalled into fragments when hit by the shock of the explosion; the fragments were neither aerodynamic enough nor large enough to perform effectively. Secondly, the blast "leaked" between the balls, reducing their velocity. A second problem was the curvature of the mine. This was determined experimentally by Bledsoe, through a large number of test firings. After Bledsoe left the project to work at the Rheem corporation, William Kincheloe, another engineer, came onto the Claymore project. Kincheloe immediately suggested using softer steel "gingle" balls, which were used in the foundry process. They did not spall from the shock of the explosive, but deformed into a useful aerodynamic shape similar to a .22 rimfire projectile. Using a homemade chronograph, the engineers clocked the balls at . The second change was to use a poured plastic matrix to briefly contain the blast from the explosive, so that more of the blast energy was converted into projectile velocity. After a number of experiments, the engineers settled on Devcon-S steel-filled epoxy to hold the balls in place. With this change, the velocity improved to . Technical challenges to overcome included developing a case to contain the corrosive C-3 explosive that would be durable enough to withstand months of field handling in wide temperature