I read some time ago that pilots loved the P-38 as a fighter. All of its guns were on center-line, so there was no "convergence angle" as on a conventional single engine fighter with guns on the wings.
The conventional layout had the guns angled in toward each other so the bullets would converge at a give point in front of the aircraft, usually around 1K yards. Any closer or further away and number of bullets on target dropped.(try hitting a target 5 feet wide with 2 guns hard mounted 25 feet apart.)
The P-38s guns were all mounted within inches of each other, and had no single "most effective" range. Doesn't matter if your 25 feet or half a mile away.
Also, apparently if you were good, you could firewall one engine, drop the other to idle, and nothing in the sky could match the resulting turn rate. (Never figured that out myself, at high rates of turn, the bank angle is is so steep the engines on a twin are for reasonable purposes perpendicular to the turn axis, so asymmetric power settings shouldn't affect turn rate, but I've never flown one.)
