XM578 152mm, APFSDS
From 1965 to 1972, the US Army conducted development program for the 152mm XM578 cartridge, which was co-developed with the prototype MBT-70 Tank. The XM578 cartridge used a tungsten alloy that was slightly denser than the British alloy, consisting of 97.5 percent tungsten and 2.5 percent binder, which had a density of 18.5 gm/cc. The tungsten alloys used in the XM578 projectile had to be encased in a steel jacket to withstand the extreme firing velocities of the 152mm gun, reducing the penetrating effectiveness of the tungsten cartridge.
A strategy was devised that called for combining ultra-lightweight plastics with titanium sabot components. These were combined with a plastic driving and sealing band that allowed insertion of the much longer KE cartridge several feet down the rifled bore of the new cannon.
With the terminatlon of the Program and the initiation of the XM-1 Tank Program, a need for a modern 105mm Anti-tank, Kinetic Energy Projectile. Picatlnny Arsenal responded to this tasking by utilizing the technology gained in the 152nwn Program - specifically the subpEojectile - and adapting it to the 105mm Gun by means of a saddle sabot.
Throughout the 1960s and early 1970s, the US Army developed a successive series of improved 105mm rounds (the primary caliber of the main gun on M-60 and developmental XM-1 series tanks) using the denser 97.5 percent tungsten alloy. The XM735 and XM774 cartridges were the first rounds developed out of the XM578 cartridge program.
A decision analysis was performed on the XM578 APFSDS projectile development program in 1973. The decision analysis differed from a Risk Analysis in that, along with assessing program risks, the decision analysis proposed alternative program approaches and compared the expected outcomes of the proposed alternatives with the basic program. Prime consideration was given to the quantification of uncertainties, examination of allocation of resources between test and design phases of the development program and to quantify the value of information obtained in a test program.
