The BAE Systems has secured a $117m (£71m) deal from the US Department of Defense (DoD) to supply 62 M777 howitzers.
This builds upon an initial order placed by the DoD in May for 63 guns and a related support contract.
The manufacturing and assembly of M777 are undertaken at BAE's facility in Barrow-in-Furness, UK. The final integration and test of the weapon system is taken up at Hattiesburg facility.
The M777 uses titanium and aluminium alloys and weighs less than 4,200kg, half the weight of conventional 155mm systems.
Both the US and Canada operate M777s in Afghanistan.