This is not off-topic mods, someone asked the question, and I responded.
The Sargeant York was rejected due to multiple reasons, most of which were technical and jamming failures.
" DIVAD called for the gun to acquire a target and start firing within five seconds (later extended to eight) of it becoming visible or coming into its 3,000 m range, and had to have a 50% chance of hitting a target with a 30-round burst. In addition to all-weather capability, it also needed to have optical aiming capabilities, including a FLIR and laser rangefinder.[6]"
"Despite the bad press and development problems, the Army continued to press for the system’s deployment as they had no other system in the pipeline to replace it. To add to the problems, another generation of Soviet helicopter and missile designs was pushing their envelope out to 6,000 meters (6,600 yds), rendering DIVADs ineffective at long range. In response, the Army announced it would consider adding the Stinger missile to the DIVAD system, leading to even more cries about its ineffectiveness.[6]
As Washington became increasingly fed up with the DIVAD’s problems, Secretary of Defense Caspar Weinberger ordered a $54 million series of battlefield-condition tests. Congress authorized production money to keep the program alive through a test-fix-test cycle but with a caveat; the funds would be released only if Weinberger certified that the gun “meets or exceeds the performance specifications of its contract.” The tests were monitored by the Pentagon’s new Director, Operational Test and Evaluation Office (DOT&E), mandated by Congress in 1983 to serve as an independent watchdog.[22] The tests were carried out late in 1984.
The results were abysmal. When the gun proved unable to hit drones moving even in a straight line, the tests were relaxed to hovering targets. The radar proved unable to lock even to this target, as the return was too small. The testers then started adding radar reflectors to the drone to address this “problem”, eventually having to add four. Easterbrook, still covering the ongoing debacle, described this as being similar to demonstrating the abilities of a bloodhound by having it find a man standing alone in the middle of an empty parking lot, covered with steaks.[23] The system now tracked the drone, and after firing a lengthy burst of shells the drone was knocked off target. As it flew out of control, the range safety officer had it destroyed by remote control. This was interpreted by the press as an attempt to “fake” the results, describing it as “sophomoric deceits”.[24] From that point on, every test success was written off as faked.[25]"
It failed to do its job effectively due to its limitations and inability to hit the needed targets.
