The AAI XM70 is an American assault rifle developed by the AAI Corporation that fires 5.56 mm flechette rounds. The XM70 was considered as an entry into the 1970s Future Rifle Program to replace the long serving M16 rifle; however, due to the high cost of manufacture, the AAI SBR was chosen instead.
The XM70 research and development was initially given to another company, but the recoil from 6 fast shots caused the gun to bounce and to flip over. Pacific Car and Foundry was awarded the contract and revised the design to 6 shots of constant recoil force. The action accelerated forward and fired at the forward point. The recoil in the rearward direction was stored in a torsion bar and disapatated in a hydraulic cylinder. It was basically a 6 shot revolver with the cylinder split into two pieces. Each cylinder wall had a different thickness for keeping balance as the chambers swung and became empty. This is explained in United States Patent US4353285. This caused the gun to sit high on the suspension until the six shots were fired automatically. While the 6 shots were firing, the vehicle sat low with the suspension compressed by the constant recoil. The vehicle then quickly left the area before enemy radar could locate the source of the artillery rounds. This tactic was called "shoot and scoot".