Had a 7:1 kill ratio if I'm not mistaken. An unsung hero along with the P-40.
Comparing Japanese and US accounts, the F4F had around a 1:1 ratio v the Zero itself in 1942, roughly 3:1 overall (bomber, floatplane, etc). In 1943 F4F's mainly met A6M's while flying from land bases in the Solomons, supported by higher performance types like the F4U and P-38, so, it's harder to compare head to head performance there, but the overall ratio didn't turn drastically against JNAF fighters until after the F4F was phased out. But, 1:1 v the A6M in 1942 was best among Allied fighter types which saw significant action that year, significantly better than the P-40's 1942 record v the A6M; again measuring by recorded losses of each side, which is generally possible in 1942.
FM-2's entered combat in 1944 and eventually did see some action against real Japanese fighters, though most of their targets were bombers and later on kamikazes (some of which were fighter types, but not really acting as fighters). The FM-2's overall claimed kill ratio was remarkable. According to Naval Aviation Combat Statistics (USN's official doc), Table 28, from Sep 1 1944-Aug 15 1945, FM-2's claimed 377 enemy a/c for 9 air combat losses. Against Japanese fighter types they claimed 183 for 7 losses. There's no way, AFAIK, in that phase of the war to add up Japanese recorded losses in all those combats, but here's an interesting example for which accounts are available from both sides:
Lingayen Gulf (Luzon, Philippines) invasion, January 1945. The invasion convoy was supported only by CVE's, the fast carriers were off striking elsewhere. The Japanese managed to mount serious air attacks, and the FM-2showed its main weakness at that stage: too slow as an interceptor. That was even a weakness of the considerably faster F6F by 1945. Kamikazes scored a number of hits after getting past the fighter CVE's CAP. But against Japanese fighters supporting the kamikazes January 8, the FM's claimed 3 'Tojo's', a 'Zeke' and 5 'Tony's' without loss. Their radial opponents were not in fact Tojo's and Zekes, but more capable Ki-84 Franks of the 73rd Sentai JAAF, along with Tony's of the 19th Sentai. 8 of their fighters failed to return per Japanese accounts, including the 73rd's CO.
Another remarkable FM-2 fighter combat occurred in the ETO. March 26 1945 FAA FM-2's (Wildcat VI's) encountered Bf109G's of JG/5 off Norway. They claimed 4 w/o loss. German records say 3 Bf109's failed to return.
In those 1945 cases, declining Axis pilot quality was surely a factor, but the FM-2 was small, highly maneuverable, had good low altitude climb, and the excellent gunnery characteristics of the basic Wildcat (esp the low nose for easy high deflection tracking). It proved a capable dogfighter against its actual opposition in 1945, in verified incidents.
Joe