The United States Navy (USN) went into World War 2 (1939-1945) with the Brewster "Buffalo" and Grumman "Wildcat" as its primary frontline fighters. However, the war quickly showcased the need for more modern fighting platforms and this gave rise to a slew of design studies put forth by the major and minor defense players of the day. While the Grumman "Hellcat" and Vought "Corsair" types ended as the service's workhorses (and ace-makers), there were other offerings which might have very well formed the new face of U.S. naval aviation.
Boeing drew up plans for what became the "Model 376" of 1943 (detailed elsewhere on this site). This single-seat, single-engine system was to be powered by the (then experimental) Pratt & Whitney R-4360 "Wasp Major" 28-cylinder air-cooled radial piston engine and the body of the aircraft was to have been rather slim and elegant. With an estimated speed of over 400 mph, the cannon-armed fighter (4 x 20mm) was to have utilized a low-mounted monoplane wing structure and tail-dragger undercarriage arrangement.
From this, the company developed an offshoot design along the same lines in what became the "Model 386". While the Model 376 was marketed for low-to-medium altitude work up to around 35,000 feet, the Model 386 was intended for sorties as high as 46,000 feet. Beyond the same powerful (and experimental) radial engine fit, the new fighter would sport contra-rotating propeller blades at the nose (2 x Three-bladed units spinning in opposite directions) - unlike the Model 376's single four-bladed unit.
All other facets of the fighter remained including its low-mounted monoplane wing members, single rudder fin at rear, and tail-dragger undercarriage. Armament was to the same as well: 4 x 20mm automatic cannons buried in the wings, two guns to a wing, and positioned outside of the spinning propeller blades and outboard of the main landing gear legs. The usual carrier-friendly qualities - folding wings (outboard of the twin wing cannons), arrestor hook - were in the plans as well. Like the Model 376 before it, the Model 386 never gained traction and fell to history.
Based on provided plans, the Boeing fighter was to have featured a running length of 41.11 feet, a wingspan of 55.3 feet, and a weight near 15,500lb. The PW R-4360 Wasp Major engine was to supply around 3,000 horsepower to the contra-rotating propeller arrangement at the nose. Estimated speed was 434 miles-per-hour (at just over 20,000 feet) with a service ceiling of 46,000 feet, and range out to 1,000 miles.