BAE Systems is to upgrade additional MK 45 naval gun systems for the U.S. Navy under the service's exercise of a contract option.

Under the $50 million option, four Mk 45s on guided missile destroyers will be converted to a fully-digital Mod 4 configuration.

The option, exercised under an initial 2015 award, brings the full value of the contract to $130 million for a total of 10 modernized gun systems.

Key updates to the Mod 4 configuration feature a mechanically strengthened gun mount and a completely digitized control system. The stronger mount allows the gun to achieve 50 percent higher firing energy, while digital control system provides more computing power through an interface similar to that of a smartphone.

The enhancements will enable the seamless integration of targeting and fire control data, such as GPS.

"The proliferation of high-volume, low-cost threats is driving the need for multi-mission, cost-effective precision fire from naval guns like the Mk 45," said Joseph Senftle, vice president and general manager of Weapon Systems at BAE Systems. "As a leader in large-caliber naval guns and precision guided munitions, our team is committed to developing reliable and affordable technology that adapts faster and reaches farther than ever before."

BAE Systems said delivery of the first upgraded gun will occur late next year. The final delivery is scheduled for 2020.