I'm going to say "no" on the F4U-4B (20mm) in WWII. I can't find exact data, so it's a best guess with what I have.
Depending on the source, I get between 296-300 B models were built. There was no A model, just plain old F4U-4 for the .50cal a/c.
First F4U-4 in combat is either April or May 1945 depending on source.
Information extracted from "America's Hundred Thousand" Francis H. Dean is somewhat confusing,
Page 507, There were 1859 F4U-4 aircraft accepted by the end of August 1945, 2050 was the total F4U-4 production through April 1946.
(The author may have intended this to show just F4U-4 a/c and not B models.)
Page 524, Vought continues low level F4U-4 production until mid-1947, producing a total of 2356, with 1912 -4's before VJ Day.
Nick Veronico's book "F4U Corsair" shows 5- XF4U-4, 2045-F4U-4, 296-F4U-4B 20mm cannon a/c & 11 F4U-4Bs ( Bat Bomb?).
I have an original Vought Tech Rep Manual for the F4U-4. It's not dated, so I don't know exactly how far along in F4U-4 production that it's accurate. Interestingly they refer to the a/c as Corsair IV and no it's not a British manual.
What it does show is a list of MCR's (Master Change Records) which shows Corsair development from the beginning, F4U-1 thru F4U-4.
MCR 379 Wing-20mm Cannon, started July 44, small batches of 20 a/c per month. 200 a/c = 10 months, July 44 - May 45 (?), see pic.
Regards,
Mike
