Help: Q on Mounting of .50 cal on submarine

Dear followers, I received the following email from Richard Pekelney, one of the crew restoring USS Pampanito (SS-383), a WW II submarine museum and memorial in San Francisco.

Pampanito in more modern times, which they are trying to restore to her late WWII condition and appearance– hence the 50 cal questions

I pose it to the larger community here for their expertise:

During the summer of 1945 (our target restoration date), Pampanito had x4 .50 cal. Browning machine guns. Until a few weeks ago we never thought too much about them, and we really do not know anything about small arms. It turns out their mounting and configuration are interesting and different than surface ship installations we have seen from the war (aircraft gun, no recoiling slide group or side slide, aircraft recoil absorbing mount). I am writing you today to ask you to take a look at the…