The order for the weapons came under a contract modification from the Naval Air Systems Command worth $7.8 million, the company said.
"General Dynamics has successfully produced the weapon system for the F/A-18 for more than 25 years," said Steve Elgin, vice president and general manager of armament systems for General Dynamics Armament and Technical Products.
"The M61A2 F/A-18 gun system continues to be relevant, affordable and extremely effective."
The M61A2 gun system is a six-barrel Gatling gun. It has a closed-loop rotary feed and can fire as many as 6,000 rounds a minute.
Additional details of the contract modification, as well as a delivery schedule, weren't disclosed but General Dynamics said the weapons would be produced at its facility in Saco, Maine.