SACO — Defense contractor General Dynamics was awarded a $14.3 million contract for quick-change barrel kits for .50-caliber machine guns mounted on vehicles, boats and helicopters.

Sens. Susan Collins and Angus King of Maine said 3,000 of the kits will be produced for the military at General Dynamics’ plant in Saco. The award brings the total to more than $42 million under the contract.

Collins called the Saco plant a critical part of the national defense industrial base. It is part of the General Dynamics Armament and Technical Products division headquartered in Burlington, Vt.