There have been multiple versions of the Gammatron. "Thunderbolt" Ross made the initiative for the military to develop this item. Initially it was designed to defeat the Hulk by bombarding the man-monster with Gamma Energy. This prototype was referred to as a Gammatron Bombarder. When the Avengers used the Gammatron on the Hulk he deflected its blasts back into the machine and destroyed it. The Assemblers thought the machine was ineffective in stopping the Hulk. However, in actuality it weakened him a great deal; and the effects were not evident until after their battle.
Later the primary purpose of the Gammatron has been to cure Bruce Banner of turning into the Man-Monster the Incredible Hulk. The Gammatron was soon modified not only to bombard subjects with Gamma bolts, but also to drain subjects of any Gamma Energy. When next fired at the Hulk, the Gammatron once split Banner into two distinct entities. Once the Gammatron siphons gamma radiation from its subject, tremendous amounts of radiation is stored within the machine. A planned release of this radiation transformed Leonard Samson, once again, into a Gamma-spawned Super-Human.