Fixed rearward-facing defensive guns - any worth in it?

[Shortround6]

Bill Gunston pointed out that the best attack position for a nightfighter was directly below the targeted bomber, but that none of the RAF aircraft had so much as window in the belly to detect that kind of attack.

Yes and no.
Depends on time in the war, what planes and even which squadrons.
Crews knew there was something going on. Not every plane hit was shot down and lost. Crews could look at the holes in a plane and figure out where the shell came from despite some
"experts" telling them it wasn't happening that way.
some planes without H2S radar wound up with a .50 cal firing down through a hatch in the floor behind the bomb bay. View have been limited and field of fire more so. How long this took doesn't get mentioned or not mentioned much. Actual kills may have been very small. Change of underwear may have been more common

 

[MIflyer]

Crews could look at the holes in a plane and figure out where the shell came from despite some
"experts" telling them it wasn't happening that way.

This could be "Survivor Bias" at work. As in B-17's did not get hit in the cockpit, engines, or aileron linkages because the ones that were hit in those areas mostly did not get back. If a BF-110, Ju-88, DO-217, BF-109, got all lined up and hit a Lanc from below using Jazz Music maybe it was all over with.

On the other hand, you know how many Allied nightfighters could do a Jazz Music job on an enemy bomber? Only one I could think of is the P-61 and that did not even apply to most of those deployed.

 

[yulzari]

Bill Gunston pointed out that the best attack position for a nightfighter was directly below the targeted bomber, but that none of the RAF aircraft had so much as window in the belly to detect that kind of attack.

Thus the Boulton Paul Defiants made similar attack positions with the extra benefit that the gunner could not only engage from a wider range of positions from underneath but also maintain fire as the bomber attempted to evade. With the pilot not having to find and keep the Defiant pointing (allowing for deflection) at the enemy but merely to be in the vicinity of the bomber, whilst the gunner tracked the target. Night interceptions were limited with only ground control information until radar was fitted to later Defiants but, once intercepted, the Defiant was the most likely night fighter in 1940/41 to shoot down the intercepted bomber being able to fire from below and to maintain effective fire against enemy manoeuvring and maintain fire longer as the gunner could track the enemy. In short the forward firing night fighter made a pass at the enemy and sought to repeat it again whilst the turret night fighter could maintain longer continuous fire.

 

[MIflyer]

Was it the Fulmar or the Albacore that sometimes featured the rear observer throwing rolls of toilet paper to discourage attackers?

 

[Engineman]

Thus the Boulton Paul Defiants made similar attack positions with the extra benefit that the gunner could not only engage from a wider range of positions from underneath but also maintain fire as the bomber attempted to evade. With the pilot not having to find and keep the Defiant pointing (allowing for deflection) at the enemy but merely to be in the vicinity of the bomber, whilst the gunner tracked the target. Night interceptions were limited with only ground control information until radar was fitted to later Defiants but, once intercepted, the Defiant was the most likely night fighter in 1940/41 to shoot down the intercepted bomber being able to fire from below and to maintain effective fire against enemy manoeuvring and maintain fire longer as the gunner could track the enemy. In short the forward firing night fighter made a pass at the enemy and sought to repeat it again whilst the turret night fighter could maintain longer continuous fire.

The Turret Fighter, in the form of the Defiant, was indeed planned to formate on the bomber and rake it with fire. Unfortunately, this usually involved the Defiant being shot back at by the bomber. In practice, the Defiant was found to have problems with engaging targets, the difficulty of the pilot manoeuvring to suit the gunners requirements of positioning and stability for his aimed shots is mentioned in reports. The turret could not fire forward through the prop disc and other parts of its own airframe, flying in a stable position usually invited return fire and the pilot could not aim the guns, so had to be talked-on by the gunner.
For Night Fighting in 1940, the Defiant seems to have led the scoring, with GCI, but kills were low. The Beaufighter started Night Fighting in late 1940 with GCI/AI and rapidly became the most effective for 1941, with forward firing guns. Targets were supposed to be visually identified before firing.

Eng