The U.S. Army began testing four prototype rifles as possible replacements for the Ml6A2 as the primary combat rifle of the US military. The prototypes were designed to meet the Army's goal of a 100% increase in average hit probability over the Ml6A2.
All four weapons featured dramatic, futuristic styling and the very latest in ammunitions technology. The prototypes from the USA's AAI Corporation and Steyr-Mannlicher of Austria both fired flechette ammunition. The AAI featured the most traditional styling of all the prototypes, while the Steyr-Mannlicher had a unique, rounded "bullpup" design.
Colt's entry was capable of firing both the standard US Army M855 ball and a completely new ammunition type, the "duplex" round. The duplex round consists of two bullets loaded nose4otail in one casing, and is designed to increase hit probability.
But the most radical of the new weapons came from West Germany's Heckler & Koch. Another bullpup, with a non-removable, variable-power sight, the H&K was a variant on the West German G-1 1 rifle. Its most unique feature was its ammo - it used the first successful caseless cartridge, a 4.92mm bullet sealed in a rectangular block of nitramine compound, 58% lighter than the M855 round then in use.
The Army announced hopes for a decision on the type of technology to be adopted by late fiscal year 1991, with the possibility that a new weapon could be in the hands of soldiers by 1995.