[Bryanw92]

http://www.urbandictionary.com/define.php?term=gundeck

This is what it meant when I was in the Navy.

[incredulous joe]

Thanks, we were discussing the fact that my son was struggling to complete his Eagle requirement for BSA and he mentioned that a lot of boys today simply “gundeck” the process toward the end. I knew what he meant, but always love the colorful navy descriptions.

[NorthMountain]

From UD:

The area on old British warships below the upperdeck, to give a false perception of the actual amount of ammuniton onboard. This is supposedly how the term was derived.

Is this saying that they'd display a bunch of powder and shot on the gun deck during some sort of official visit, but have (nearly) empty magazines?