Now that I am back on my PC & not my mobile, here is the direct link to the report: http://www.wwiiaircraftperformance.org/f4f/f4f-3-1845.pdf Sorry, but WW2aircraftperformance was not displaying correctly on my cell(I got the drop down box for the US, but there was nothing in it) The two .30s & two .50s are mentioned on page 2, and firing trials on pages 7-8. The report tells of the gun testing with 100 rounds being fired from each gun on the ground, and 1,300 .30cal & 2,020 .50cal rounds were fired in flight. The report goes on to state that the two .50cal wing guns proved to be very problematic in flight. They installed a large diameter roller at the mouth of the ammunition box in hopes of alleviating the problem, but it failed. It was finally decided that the problem was improper timing of the guns. The guns were correctly timed and tested on BuNo. 1848, and the problem was solved. However, no more is mentioned on the .50s on BuNo. 1845, so I would hazard to guess that the guns were removed as the aircraft was under evaluation for several months. The one thing that I wish was mentioned in the report is the amount of ammunition carried for the guns of BuNo. 1845. It says that the .50s of BuNo. 1848 had 450 rounds per gun, but nothing on BuNo. 1845.