I'll hazard a guess but AG vets, please correct me.
On a cargo-only Liberty ship, there would have been four 20-mm guns at the flying bridge level, one in each corner. There would have been two more 20-mm guns flanking the 5" gun in the stern, and two more in elevated gun tubs on the fore deck, port and starboard, about one-third of the distance back between the bow and the superstructure. That accounts for eight of the nine guns mentioned in the log you have. My guess is that the ninth 20-mm would have been the bow gun, where more often a 3" or 4" gun would have been positioned. Possibly this ninth 20-mm was later replaced by the more standard 3" bow gun. Who knows, maybe there weren't enough of the larger guns to go around when the ship was launched? I don't know of any photographs or other documentation that would support this so it's only my guess.
See this photograph of the JEREMIAH O'BRIEN as a good indication of the location of guns on a typical cargo-only Liberty ship: http://www.ssjeremiahobrien.org/ssjobrien-2.jpg. In this case, the bow gun is the standard 3" gun, not a 20-mm, but one can make out the locations of most of the 20-mm guns in this photo if one knows where to look and what to look for.
On Liberty ships that carried both cargo and troops, such as the JOHN W. BROWN, on which I volunteer, the configuration was somewhat different. The BROWN has two 3" guns flanking the 5" stern gun, replacing the two 20-mm guns in the stern described above, two more 20-mm guns flanking the 3" bow gun, two 20-mm guns in elevated gun tubs on the after deck, port and starboard (but no gun tubs on the fore deck), plus the usual four 20-mm guns on the flying bridge. (So: one 5" gun, three 3" guns, eight 20-mm guns.) But I assume the ROBERT J. COLLIER was a cargo-only Liberty ship, as was true with the vast majority of these ships.
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