It was designed to be used with approximately 6.5 lb (2.9 kg) of GB or VX nerve agents.
[7] Shortly after the discovery of VX in 1952,[8] the U.S. Army Chemical Corps began experimenting with employment systems for the newly discovered nerve agent.
The M121A1 was standardized in 1961 as a modified version of the original projectile with the additional capability of transporting VX as well as sarin.
[9] The M121 and M121A1 have never been used in combat and remaining stockpiles are currently being disposed of in accordance with the 1997 Chemical Weapons Convention.
The M121A1 is identical to the M121 with the exception of it using a larger fuze assembly, which makes the entire projectile 28.8 inches (73.2 cm).