Comment on my post above: Either this is a USS ship or the Navy has started to put Navy armed guards aboard its USNS ships. Something of which I would whole heartedly approve. But it is highly unlikely the the civilian crews on USNS vessels would be allowed to man 50 cal machine guns. I admit I have been out of the loop for a few years.
All U.S.N.S. ships are civilian maned have limited amount of DEFENCE weapons. The 50 cal. was maned by a team of active military.I have sailed on that ship and have nothing but praise for the crew.