British WW2 Heavy Bomber Armament

[Deleted member 68059]

I "lost" this file for years because it has an archive title which is nothing to do with the contents. Found it again by accident a few days ago.

The file is an Air Ministry file, so, of course is probably a fraction less self critical than it could be, but still will I think really add some factual explanations for the apparently ludicrously poor armament of RAF bombers.

 

[Snautzer01]

Thank you. Will read a bit later

 

[Engineman]

Very good reading! So, no doubt really, a decent 20mm with a better sight (or method of seeing at night) was needed. .303 was the scatter-gun.
Makes the Mosquito bomber look a very, very good solution.

Eng

 

[taly01]

I fully read the pages on general history/ defensive armament, but not plane type notes. Nice analysis. My take is that WW2 bomber guns were mostly scare weapons, and that was their more important job to deter & disrupt enemy attacks than shooting down planes. I agree with the logic that says 4x.303 turret is as effective as .5/20mm after taking into ROF hit probabilities.

I'm mostly interested in j-aircraft atm, and the JNAF were the first country to use 20mm bomber guns in large scale, by 1940 in the G3M2, however they were pintel mounted with ring and bead sites and 30/60 round magazines, and with a reduced ROF option 120-500rpm. However the G3M and later G4M "Betty" did shoot down enemy fighters (confirmed kills by both sides) but had trouble detering attack runs by enemy fighters. You could say they chose the 20mm for shoot downs Vs deterrent only, which fits with Japanese military doctrine.

This is a long way of showing the British analysis of 20mm vs .303 was proven correct for WW2 era.

 

[yulzari]

I "lost" this file for years because it has an archive title which is nothing to do with the contents. Found it again by accident a few days ago.

The file is an Air Ministry file, so, of course is probably a fraction less self critical than it could be, but still will I think really add some factual explanations for the apparently ludicrously poor armament of RAF bombers.

Excellent refind. Thank you. The most interesting thing for me is the clear intention of the Air Ministry to acquire 0,5" machine guns and they had clearly been making active arrangements to both buy Breda guns and to buy an FN Browning production line for UK production. Efforts, when these fell through, to acquire US made Brownings were not possible in volume until much later on in the war.

It strongly refutes typical post war comments about the RAF ignoring the interim 0,5" gun. Fighter Command had decided to jump to the 20mm cannon for their fighters (quite sensibly) but these were not feasible for wartime bombers as explained in the minutes above. The RAF, it shows, actively considered both 0,5" and 20mm cannons and found them suited to different tasks. The normal airborne FN guns came in 13.2mm as did the Breda so the RAF had looked to standardise on the 13.2mm gun rather than the US 12,7mm so would use the Hotchkiss Long 13,2x99mm cartridge not the Browning one for both the Breda and the FN. IIRC Hawkers were impressed with the 4x13,2mm guns for Belgian production Hurricanes. It is not at all impossible that these would have been a fighter alternative were the UK production line to have been set up. Looking at the effectiveness of FN's 13,2mm HE shell compared to the US 12,7mm and it's lighter weight and better rate of fire in 1940/1 I can see that it seems a superior choice and quite suitable for the fighter role were the 20mm cannon a production or installation issue.

It is hardly curious that there is no mention of the trials of the 40mm Vickers in a mid upper turret.

 

[A.G. Williams]

I am a bit confused....

The FN 13.2mm was available as an aircraft gun (air cooled, high rate of fire), firing 13.2 x 99 ammo which was almost identical to the .50 BMG ammo (12.7 x 99). The FN gun was simply the Browning design with some improvements.

The 13.2 mm Breda was not an aircraft gun, it was mainly used as a light AA gun and was also fitted to some AFVs. It was basically a Hotchkiss made under licence and firing the same 13.2 x 99 ammo. The Japanese Navy used two guns chambered for 13.2 x 99: the Type 96 AA gun (a Hotchkiss) and the Type 3 aircraft gun (a Browning).

The 12.7mm Breda-SAFAT was a completely different design and fired smaller and less powerful ammo (12.7 x 81SR). This ammo was the export version of the Vickers .5 inch ammo - the UK never adopted the aircraft version of the .5 inch Vickers gun, but it was used as a light AA gun by the RN and fitted to a few light tanks.

Certain other guns were designed to use 12.7 x 81SR ammo, of which the best was the Japanese Army Ho-103 which was a scaled-down .5 inch Browning, smaller, lighter and faster-firing. Would have been perfect as a turret gun...