completely, requiring a complicated and slow gas-driven scavenging system. They were also liable to detonate if the vehicle was hit. Firing the gun caused such a large recoil as to result in failures in the delicate missile firing electronics on the tank. These problems, in combination with the lack of suitable targets, resulted in their deployment without the complex missile system. The Shillelagh was considerably larger than a conventional round, so only a small number could be carried. Typical loads consisted of only nine missiles and twenty M409 HEAT rounds for short-range use. In addition, the missile proved to have a very long minimum range. Due to the layout of the vehicle, the missile did not come into the sight of the gun/tracker system until it was from the vehicle, at which point it could start to be guided. Because of its maximum range of about , the system was only effective within a fairly narrow span of combat distances. While the maximum range of was acceptable, the Army thought that it could and should be improved. Ford received a contract to develop a longer range version in 1963, and returned a slightly larger design the next year. Test firing of the new MGM-51B started the next May, and production began in October 1966. Besides the changes to the missile, the gun was modified. In testing it was found that the key slot in the gun led to cracking after firing only a few shells. After further study, a version with a shallower slot and new barrel was selected, creating the M81E1/MGM-51C. The new missile was about long, about in diameter, and weighed . It remained in production until 1971, by which time 88,000 had been produced, probably in anticipation of use by main battle tanks (below). Although it is commonly asserted that some missiles were fired during the Gulf War, the US Army denied this. M60A2 "Starship" Even with its problems, the system had shown that it could be used by an airborne tank to destroy a main battle tank. The question of whether or not it could fill its original role as the main armament of all tanks was still open. The Army had originally started development of a low-profile turret with a short barrel for their existing M60 tanks in the 1960s, but did not place an order for delivery until 1971, when the main problems with