Congressional clearance for the package worth around $647 million was sought last month.
This became necessary because the US branch of the UK-based BAE Systems had developed several systems in the gun, including the Laser Inertial Artillery Pointing Systems and associated parts, equipment, training and logistical support.
FMS is the government-to-government method for selling US defence equipment, services, and training.
Gallagher said the gun weighed just 4.3 tonnes, while its nearest competitor weighed 14 to 15 tonnes. It is lightweight because it is made of titanium which means it can be loaded in a helicopter and transported to heights, including mountain tops. It has been used in Iraq and Afghanistan by US and Canadian forces.
Gallagher said BAE Systems -- which has tied up in a joint venture with Mahindra & Mahindra for a Rs 99.4-crore joint venture called Defence Land Systems India that will produce an anti-land mine vehicle -- is seeking partners in the naval sphere along similar lines, to augment capabilities of the Indian Navy.