09/30/2008. The FM-1 produced under subcontract to Grumman by Eastern Aircraft Division of General Motors, at Linden, New Jersey, was externally identical to the F4F-4. The Pratt & Whitney R-1830 Twin Wasp was retained, but wing armament was reduced from six to four 0.5 in (12.7 mm) guns, while the ammunition capacity was raised.
The first of 1060 FM-1s (BuNos. 14992 to 15951 and 46738 to 46837) was flown on August 31, 1942, 312 of these were delivered to the Fleet Air Arm of the RN, s/n JV325 to JV636, designated Martlet Mk.V, these were redesignated Wildcat Mk.V in January 1944.
