Beaufighter question – why six guns?

I’m glad I asked, because this has turned out to be a really interesting thread. Thanks, everyone!

Adrian

big or little?

I could never work out the reasoning for the weird mix of 20 mm cannon and .303 machine guns…

a) Lack of confidence in the cannon (true enough about the early cannon Spits)
b) The “old guard” saying that cannon are unnecessary and 303’s worked fine for me etc etc.
c) We’ve got the space so let’s stick a few 303’s in for good measure (or in the case of the Spit leave them where they are?
d) All of the above?

I can’t speak for the Beau, indeed I’d like to know more about the addition of .303s to it, therefore I plead guilty of perpetrating thread drift; I’ll take a stab at an answer for the Spitfire:
D) All of the above
At least, at one time or another each of the answers can be supported.

The initial side-mounted, drum-fed “b-wing” installation was not a great one, and limited the firing time for the cannon (assuming they would continue firing!) The “continuous feed” was being developed, but meanwhile re-fitting 4 .303s was both a useful supplement to the cannon and insurance that you’d at least have something to shoot with.

A mix was favoured at least by some, because when fighting against an Me-109 one .303 round in the radiator could be just as much trouble for Herr Emil as could a bullseye with the 20mm. When the Fw-190 made its appearance the .303 seemed far less useful. As for bombers, arguments raged.

As Graham points out, 4 20mm turned out to be a bit much for the Spitfire until later, and initially there was quite a bit of uncertainty about whether there’d be enough Hispanos to go around. Joe Smith’s “universal wing” was an inspired choice, side-stepping the problem of changing requirements. Incidentally, one further advantage of this wing that is seldom noted is that the inboard (4) .303s, if going with the 8 Browning option, could have more rounds per gun, which Supermarine had also been asked about somewhere along the way.

bob

Coastal Beaufighters had the mg removed for extra fuel tanks.

For the Beau, I suspect it was simply a matter of the more firepower the better and you couldn’t readily get cannon in the wings. The Air Ministry believed in four cannon as their prime air-to-air armament, but mg made more sense in a ground-strafing role, so a mix of armaments made sense for a mulit-role type (as all should be, to some extent!). The same principle would presumably apply to the Mosquito.

For the Spitfire, the four outer mgs were retained with the inboard cannon because carrying four cannon (specifically the heavy Hispano) proved rather too much for the aircraft, lowering performance and affecting handling. Two cannon was not considered adequate firepower.

I could never work out the reasoning for the weird mix of 20 mm cannon and .303 machine guns in the Beaufighter, Spitfire etc. I think I remember hearing somwhere that the ballistic charcteristics were pretty different (which would make sense). If so was it

a) Lack of confidence in the cannon (true enough about the early cannon Spits)
b) The “old guard” saying that cannon are unnecessary and 303’s worked fine for me etc etc.
c) We’ve got the space so let’s stick a few 303’s in for good measure (or in the case of the Spit leave them where they are?

d) All of the above?

Didn’t the early night fighter Beaus have the 303’s removed because of the radar array in any case?

Thanks Niall, makes sense.

Apart from the interesting side benefit mentioned earlier, did the guns have to be counter weighted in the other wing?

I was wondering if it was down to production economy of using the Beaufort wing, but surely the machine gun installation and feed system in itself would have required a greater structural redesign than relocating the lamps?

Quite so, but I think the position was that to incorporate 6 guns would take a certain amount of effort (but probably little modification to the tooling since that area is really just fresh air in the Beaufort wing) whereas to fit 8 would require the same effort plus some more to rework the leading edge (and spar?) where the landing lights were. So a compromise was made.

I was wondering if it was down to production economy of using the Beaufort wing, but surely the machine gun installation and feed system in itself would have required a greater structural redesign than relocating the lamps?

The rationale behind the “Beaufort Fighter” was to provide a cannon fighter at a time when the need for one was seen as urgent, but the Whirlwind (which hadn’t yet flown let alone been ordered) appeared to be unlikely to enter service before mid-1940. The appeal of the Bristol proposal (vs. say Supermarine’s Type 327 or any other all-new design) was that it used as much of the Beaufort tooling as possible, and therefore could be put into production quickly.

Originally the proposed design carried just the four Hispanos in the fuselage and no wing armament. When the wing-mounted Brownings were asked for, late in the day, Frise told the Air Ministry that to fit eight guns would require rework of the Beaufort wing tooling because the outer port guns would clash with the landing lights. So, as a compromise and in order to accelerate production, the ministry accepted six guns: 2 port and 4 starboard.

As I understand it the extra weight was also put into one wing to counter ‘swing’ on take-off and landing.

Many many years ago I was standing in front of the RAF Museum’s Beaufighter example discussing this very point about the extra guns in one wing with my former father-in-law. A voice behind us informed us he was a former Beaufighter pilot and he had encountered another problem: “We never fired all ten guns near to stalling speed as they acted like retro-rockets and carved 50mph off of the speed…”

Well that was something I didn’t know!

The Aussies arguably came up with the most sensible solution with the DAP-built Mk.21’s. They had four .50 Brownings, two in each wing, plus the underbelly cannon.

According to Wiki, the assymetric armament was down to the landing light installation in the port wing – which begs the question, wouldn’t it have been easier to have moved the light?