Popular Mechanics had an interesting article on fighter aircraft armament in 1942. They tried to reduce firepower to horsepower, by rating horsepower of the various armaments, an admittedly inadequate metric.
The Germans and Japanese favored heavier caliber guns with lower rates of fire, good for lobbing shells at bomber formations from a distance, and carrying a high explosive charge in order to do damage when they hit. 30-caliber seems like a pea shooter by comparison. The Americans tended to use Browning 50-cal for fighters, with six or eight on the wings. The P-38 had all its guns in the center nacelle, firing straight ahead, and two 20 mm cannon, which gave it awesome firepower.
The USAF (Then Army Air Corps) had a lot of pre-conceived notions about fighter design. On such notion was that pursuit planes (fighters) weren’t to have mechanically supercharged engines. Another was armament. It was felt that cannon weren’t required and so the USAF went pretty much the entire war without a decent aerial cannon.
The exceptions were the P-38 & P-39 programs which were both conceived as interceptors. The P-38 did get saddled with turbo-superchargers because that was all the USAF had funded, but the P-39 tinkered with a mechanical supercharger that was later deleted. But on account of their roles as bomber killers they both got cannons in the nose. It really wasn’t until Packard began building the Merlin V-12 under license that the USAAF got a competitive fighter engine with a 2-stage intercooled supercharger. Prior to that only the American radial engine designs really were competitive from a horsepower standpoint.
The P-38 had 4 .50 caliber Browning mgs and 1 20mm cannon all in the nose of the center nacelle.
Having 4 mgs might seem as a disadvantage as most US WW-II fighters had 6 .50 calibers. However by having the guns clustered around the 20mm canon the firepower of the .50s was concentrated and the pilots did not have to worry about having to be at the optimum range where the wing guns met at.
Regards
alfa6 ;>}
The P 38 had four .50’s and one 20mm.