Spitfire Armaments

The US have had problem with quality of Hispanos they were producing, not with quantity. Wikipedia article references that with the book available here.

wuzak said:

Why 6 or 8? I guess the question is are 4 x 0.50" HMGs sufficient? I suppose going into 1941 the opposition for day bombers in the UK will be mainly fighter-bomber types, rather than bombers with heavier armour.

Also, they are replacing their cannons with 2nd or 3rd best choice. There have been many debates on this site as to the comparison between the destructive power of the 20mm Hispano vs the 0.50" Browning. Some suggest that the Hispano was 3 times as effective as the 0.50", so replacing the two 20mm would require 6 0.50"s for equivalent effectiveness.

Remembering that the first few Kittyhawk Is had 4 x 0.50", but later ones had 6 x 0.50". And the P-51 went from 4 in the -B to 6 in the -D.

Click to expand...

Once engine power is sufficiently up (two-stage Merlin, any Griffon), the 6 HMGs should not be that a problem.
The 1st P-40s (Tomahawks) were using 4 LMGs in the wing. Wing endured slight modifications (weight cost ~100-120 lbs) so it can have installed 6 HMGs and their ammo. The P-51 went from 4 LMGs and 2 HMGs to all 6 HMGs in the P-51D. Also carried 4 Hispanos, of course.

Shortround6 said:

I believe it was out board but in any case it went under.

Photo of the two guns installed in the wing certainly shows that TWO .50s will NOT fit in the space of one 20mm. Thank you/

Click to expand...

I admit my comment was based on the Hurricane. If with a bit of imagination they could squeeze 2 x 20mm into a space that originally held 4 x 0.303 I was thinking that they might be able to do the same with putting 2 x 0.5 into 1 x 20mm. My mistake

Was not the original 8 .303 browning armament actually highly effective? I have watched so much old gun camera footage. The German bombers looked like they were being shredded by the high volume 7.7 rounds , so much camera footage just shows them coming apart. Also, when I see early me-109 footage firing on a spitfire, it is usually them missing completely with the slow firing low velocity drum fed early mg/ff 20 MMS. This subject has intrigued me for years. Also in this footage, it looks like the German mine shells are just bursting to little effect when they hit. I can't imagine even a modern aircraft standing up to 9,600 rounds per minute of rifle caliber ammo. Just my thought .

Jonnyboy369 said:

Was not the original 8 .303 browning armament actually highly effective? I have watched so much old gun camera footage. The German bombers looked like they were being shredded by the high volume 7.7 rounds , so much camera footage just shows them coming apart. Also, when I see early me-109 footage firing on a spitfire, it is usually them missing completely with the slow firing low velocity drum fed early mg/ff 20 MMS. This subject has intrigued me for years. Also in this footage, it looks like the German mine shells are just bursting to little effect when they hit. I can't imagine even a modern aircraft standing up to 9,600 rounds per minute of rifle caliber ammo. Just my thought .

Click to expand...

Eight .303-inch Brownings could certainly be devastating - but the type of target really comes into play. Also, 9,600 rounds per minute is certainly impressive - but holding a target in a proper gun solution for enough time to build up a lethal density is a more important question.

Going by a handful of gun camera films isn't really a scientific approach. Sample size is a primary issue. Judging damage from a few frames of grainy footage is a bad idea. A superficially devastating round could do little damage, while a round that discretely impacted between picture frames could do devastating internal damage with no apparent effect (eg: kill the pilot).

Your observations on the German 20-mm vs. Browning .303-inch are certainly reasonable. Point-form summation would be; easier to hit with Browning battery, better results from a hit with a 20-mm. Jabs versus haymaker.

20-mm explosions or the results thereof might not always look too impressive but keep in mind the hail of invisible (to the camera) fragments being sprayed inside the targeted aircraft.

That said - the British were critical of their own early 20-mm Hispano fuzes and early Luftwaffe fuzes for detonating too early (on the aircraft skin), wasting much of their effect.

The decision to adopt the eight gun fighter, with eight rifle calibre machine guns, was based on considerable research. It was estimated that given the short firing time a pilot would get at the new high speeds of engagement eight guns would be required to deliver a lethal weight of fire. This worked in the mid to late thirties, but early in the war the Luftwaffe started fitting ever increasing amounts of armour to its aircraft, bombers in particular, which negated the earlier calculations. There are reports of bombers returning to bases in France with literally hundreds of .303 strikes.
The adoption of cannon armament became a priority for the RAF/Air Ministry. The story of the problems with early installations in the Spitfire is well known, but was initially a stop gap solution. The plan was to lift four cannon with a single engine fighter, the Hawker fighter that would become the Typhoon, but that too had well known development problems and never replaced the Spitfire in the fighter role. It meant a reprieve of sorts for the Whirlwind, but that was never going to be a solution in the long term, sorting out the Spitfire was.
Cheers
Steve

I'd add that research continued throughout the war. So called 'Lethality and Vulnerability Testing' was carried out at Orford Ness throughout the war. Orford Ness is better known as the station where the early RDF research was carried out before the war and where the ballistic testing of Britain's atomic bomb were carried out post war.

The 'Lethality and Vulnerability Testing' is best explained by Bert Smith, an RAF fitter, posted to Orford Ness from an operational squadron in 1942. The pupose of the testing was,

"...to attack captured enemy aircraft with our airborne weapons and our aircraft with the enemy's airborne weapons, the results providing essential data for those responsible for identifying and meeting the operational needs of the Service. At its simplest, a trial could be carried out with just a gun and a target, but additional information such as velocity and altitude of the projectile on impact, potential to inflict damage or injury on impact, effects of slipstream etc., might also be required. Sometimes high speed photography would be used to record the sequence of events after impact."


They certainly investigated the effects of shrapnel, particularly relevant after the invention of proximity fuses. They also investigated the internal fragmentation (spalling) characteristic of armoured plate or windscreens. Some supposedly bullet proof materials actually caused worse injuries to aircrews. Out of date London telephone directories were used to measure penetration!

Penetration of fuel tanks and other vulnerable areas was investigated. Fuel tanks were more likely to rupture when struck by an unstable round, the greater the yaw the worse the damage. It was discovered that simply wrapping high pressure oxygen cylinders with a layer of wire virtually eliminated any tendency to rupture.

This operational research is a topic in itself. The RAF, more than any other Service, was keen to take the advice of the 'boffins' (a term coined at Orford Ness). It was a relatively new service and employed the cutting edge technology of the day. It needed all the help it could get

Cheers

Steve

fastmongrel said:

Madsen made 20mm and 23mm guns for aircraft use. There is also the BESA 15mm. I know nothing about rates of fire or weight maybe someone has the figures.

Click to expand...

From what I read doing some searches (today actually)...

• Madsen 20
  • Muzzle Velocity: 900 m/s
  • Refire: 400-500 rpm
• Madsen 23
  • Muzzle Velocity: 720 m/s
  • Refire: 400 rpm