swampyankee
Chief Master Sergeant
- 4,031
- Jun 25, 2013
In one of his articles, Tony Williams stated that actual air combat ranges, fighter-to-fighter, in WW2 were less than about 200 meters.
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
The trouble was that the Oerlikon came in 3 flavors and wasn't exactly trouble free either.
You had the short case guns 72-80mm case length the FF series, the FFL series with 100mm long cases and the FFS with the 110mm case (this became the famous AA gun) Weights went around 24-26kg then 30 kg and then 39--48kg for the big Oerlikon.
Some of the Oerlikons required greased ammunition to function and that was NOT looked on with favor at high altitudes with freezing temperatures.
Turns out the the Hispano also needed greased ammunition but when initially offered it didn't. Some of the cycle rates quoted for the mid 30s Oerlikons were a little on the optimistic side. But then some of the initial figures for Hispano were on the high side. At least one bbok claims the Hispano 404 was offered at 700 rpm vs the Oerlikons 520 -500-470 depending on model. French service HS 7 & 9s (licensed Oerlikons) were rated at 360-420 rpm.
If you want the velocity and hitting power of the Hispano then you need the Hispano. With similar weight shells the Hispano had a MV of 850-880 m/s the aircraft Oerlikon FFS had a MV 830m/s, the FFL series was 675-750 m/s and the FF was 600m/s.
British and Americans might have bought a shell firing gun sooner than the Hispano but it would have been a lower muzzle velocity, slower firing gun.
better in 1940-41 maybe but not as good in 1943-44-45 let alone post war.
Oerlikon 20mm cannons coming in 3 flavors was opportunity, not a problem
My suggestion for buying those is not based on some mythical properties of their cannons, but because they solve a problem of a comodity that can't be bought - time. Namely, if a deal with Oerlikon is struck in 1935, there is no reason for not having cannon-armed Hurricanes and Spitfires by 1939.
As above - not an ideal cannon, but what works and what is available.
It will not require rocket science to introduce the FFF Mod.XY that fires a 100 g shell, at 700+ m/s, and have four of those vs. two Hispanos or FFS for same weight penalty.
True but for the British (and the Americans) there was some parts commonality/manufacturing tooling between the initial versions of the Hispano and the later fast firing ones. Changing the entire gun and ammo (and the Germans used the same projectiles in the MG/FFM and the MG 151/20) means you wasted a lot of money/time on an interim gun if it has limited applications.That is true for any gun/cannon worth talking about. People started with M2 BMG, MG FFM, Hispano II and Shvak, and ended up with faster-firing BMG, MG 151/20, Hispano V or B-20, with even better wepons in pipeline.
Ok but...............
TANSTAAFL
Without coming up with a way of making shells like the Germans reducing the weight of the shell/projectile pretty much means cutting out part of the middle/payload. Fuse and base stay the same. Your 100 gram projectile might only hold around 60-70% of the explosive/incendiary instead of the 78-80% that the weight reduction suggests. You need more shells on target (fired) to get the same effect.
You also run into the poor down range ballistics problem. Short stumpy projectiles having a poor ballistic coefficient. Going by the German figures their 115-117 gram projectile (already worse than a 128 gram projectile) slowed down from 720m/s to 552m/s at 300 meters while the 92 gram projectile slowed from 695m/s all the way down to 432m/s at 300 meters. I would note that the German mine shell was long for it's weight which helped the fineness ratio.
A 100 gram at 700m/s is going to be a close range gun/projectile combination. Kinetic energy rounds (AP) aren't going to be worth much. The muzzle energy of the German 20mm MG/FF ammo was under 1/2 the energy of a 20mm Hispano round.
Russian 20 X 99 had it's MV of 860m/s to help out.
You could get cannon armed Hurricanes and Spitfires but it requires use of the retrospectroscope and very good timing. With the British crappy propellers and the Merlin limited to 880hp (and that required at least the two pitch propeller) for take-off on 87 octane fuel you have a narrow window of opportunity in which a lightweight, slow firing, low velocity cannon makes sense for the British.
If you really want to improve things for the British increase the production of .303 MK VI incendiary ammunition.
During the BoB it was reported that out of 8 guns 3 were loaded with ball, two with AP and two with MK IV incendiary tracer. Only one gun had MK VI incendiary. In later sets against the ubiquitous Blenheim test targets it was found that the MK IV set fire to the fuel tanks on 1 out of ten rounds fired.
The MK VI set fire to the tanks with 1 out of 5 rounds fired. German 7.9mm API didn't set fire to the tanks at all.
Late war Spitfires carried two guns loaded with AP and two guns loaded with MK VI incendiary. !/2 the number of bullets but what bullets there were were more effective.
True but for the British (and the Americans) there was some parts commonality/manufacturing tooling between the initial versions of the Hispano and the later fast firing ones. Changing the entire gun and ammo (and the Germans used the same projectiles in the MG/FFM and the MG 151/20) means you wasted a lot of money/time on an interim gun if it has limited applications.
In the time when other people are struggling to beat 700-800 HP mark (1936-38), Merlin III is king of the hill that sorts out the TANSTAAFL problem.
Yes three years is a long time, it saw the adoption of the constant speed propellers on British fighters and saw the introduction of 100 octane fuel which allowed the Merlin XII engine used in the Spitfire II to be rated at 1175hp for take-off.Three years is a long time - France fell within a month.
My two 'slow-firing' cannons have 80% greater RoF than one Hispano cannon found on French fighters, or 100-120% greater than one French Oerlikons (= HS 7 and 9). while Germans have a token number of cannon-armed fighters. My cannons can also use 75 or 100 rd container, Oerlikon was offering the 75-rd type for Spitfire in late 1930s. I've suggested the reduced weight ammo for the FF to improve the MV.
Problem with fuel tanks is that they represent just a fraction of aircraft's volume, cannons work well on any part of aircraft. Was Blenheim's tank with any kind of protection on the test?
I did not suggested that, after Oerlikon is accepted, people should buy Hispano. Nor that Oerlikon will have limited applications.
Most other people adopted either constant speed or variable pitch propellers during this time period. This allowed for more power to be used for take-off and initial climb. In both the Hurricane and Spitfire the Merlin was held to well below max RPM in both climb and level speed at lower than optimum altitudes.
If you restrict the Merlin to 2200rpm or under below 3000ft due the fixed pitch prop a lot of power advantage disappeared. You had to get the fighters off the ground. That is one reason even the two pitch prop cut the take-off run by over 100yds. They could increase the RPM considerably even if the boost stayed the same.
WHile your proposed guns are lighter this poor take off performance may be one reason the AIr Ministry favored twin engine planes for carrying 20mm cannon in the late 30s.
Yes three years is a long time, it saw the adoption of the constant speed propellers on British fighters and saw the introduction of 100 octane fuel which allowed the Merlin XII engine used in the Spitfire II to be rated at 1175hp for take-off.
The British first expressed and interest in the Hispano cannon in 1935. In peace time things moved slow and it took a while to sort out licence agreements, convert metric drawings to imperial measure, set up production lines and so forth. The British MARC company was formed on paper on Jan 11th 1938. Title deeds for plots of land for buildings were recorded in June of 1938 and machinery was purchased in both Britain and the United States. The official opening of the factory was in Jan 1939 and the Duke of Gloucester fired the first British HS 404 at the opening ceremony. A design office was opened about the time France fell and Captain Adams made a trip to the French factory to obtain the blue prints for the belt feed system.
In addition to the original factory/buildings, a 2nd factory was built in the same town (Grantham), a 3rd was opened at Newcastle-under-Lyme directed by BSA, a 4th at Poole and the Enfield Royal Small Arms facilities also participated in HS 404 production. This last shows why some weapons or programs didn't change quickly, There was a large investment in tooling and expertise in manufacturing an existing weapon.
Please note it took the Japanese around two years from getting the licence to actually using the Oerlikon guns.
Well, you may need some of the higher rate of fire to deliver the same amount of explosive per second. A Hispano gun was delivering about 50-55 grams per second with a drum/belt of 50% HE/50% other ammo. If you cut your shells down to 6.5 grams of HE content you need a rate of fire about 60% higher (16 rps/960rpm) do deliver the same amount of HE. And as noted the kinetic energy is rather lacking. British in the early part of the war often mixed what they called "ball" ammo in with the HE rounds. This was basically the HE shell body without filling and a steel nose cap instead of fuse. If it hit sheet metal it did next to nothing (poked a hole) but if it hit structural parts, like spars, mounting flanges/plates and the like it often broke them. The round you proposed has around a 40-45% advantage over a .50cal machine gun but they get closer together with increasing range. The Hispano has roughly twice the striking power near the muzzle and the difference gets larger with range as the Hispano's heavier projectiles don't slow down as much.
Since all these cannon used ammo of roughly the same diameter, 22mm for the Oerlikon cases at the widest part vs 25mm for the Hispano the size of the drums for a given capacity is going to be very close. Maybe you can shorten the length by 30mm or so.
...
increasing ammo capacity of drums means bigger lumps and bumps on the wing. Maybe you could get 68 rounds of Oerlikon ammo into a 60 Hispano drum. 60 x 3mm gives you 180 mm of space.
The fuel tanks were British standard self sealing tanks. German 7.9mm incendiary (non AP) worked about as well as the British MK IV, fire caused about 1 in 10 rounds fired. Guns were fired from 200yds(183 meters) astern of the Blenheim.
No projectile works equally well on all parts of an airframe. 20mm HE hits in certain areas of the wing/fuselage can make impressive looking holes by removing sheet metal but might not cause structural failure. That was one reason for the early British use of 'Ball" ammo, both the British and Germans had fuses that were too sensitive early in the war and the shells exploded on impact with the skin and did not penetrate inside to destroy vital parts. Both sides developed better fuses. When that happened the British stopped using ball/inert projectiles. A later British round was the AP incendiary. Pretty much a standard HE shell body filled with incendiary mixture and fitted with a hardened steel nose cap instead of a fuse. If it didn't hit much it went right on through, however it would punch through light armor or structural components and as the shell body broke up it would scatter the incendiary payload.
Bombers have a lot more empty space than fighters and small explosions several feet away from vital parts may not damage them with any certainty.
But the short Oerlikon will have limited application. Much less useful for both ground attack and shipping stikes. Please remember that shipping stikes include barges, fishing boats, and small coastal freighters and not just warships. And as aircraft get larger and faster ( faster means higher loads which means a more rugged structure) you are going to need more powerful ammo to take them down quickly.
...
The Bendix corporation in the United States was in negotiation with Hispano-Suiza even before the gun showed up on US soil but after Hispano Suiza raised the price twice over the initial price Bendix gave up. Price for basic rights (not including royalties) had gone from $80,000 to $500,000 to $2 million. The US government got involved and a deal was worked out but not until Dec 1938. Bendix completed the first contract for a mear 33 guns by April of 1940.
These were used in testing and for samples to US aircraft companies working on prototypes for the US Navy. The Army showing much less interest (they had their own 37mm). Please note that Bendix was supplying certain parts to Hispano-Suiza for their engines so there was some sort of relationship between the two companies.
In one of his articles, Tony Williams stated that actual air combat ranges, fighter-to-fighter, in WW2 were less than about 200 meters.
Hello MIFlyer,
The British probably agreed with you because the while the Spitfire Mk.IXc had 2 x 20 mm and 4 x .303, the Mk.IXe replaced the .303s with a pair of .50 caliber Brownings.
When comparing energy, one has to also consider at what range the target will be. At the muzzle, the .30-06 has more energy, but at a distance, the .303 British typically retains velocity better because the bullets tend to be heavier and with a boat tail. In addition, military .30-06 tends to run a bit less velocity than commercial .30-06, so Gun Digest may not be the best reference.
- Ivan.
The table posted here shows that more than 83% of kills made by Soviet fighters were made at distances of up to 200 m.
I not going to hunt up the reference, but I think Tony Wiiliams said one of the reasons for the mix of 20 mm and 0.5" in some Spitfires was.....?????
What was the thought you were trying to express and what was the reasoning?
- Ivan.
An interesting quote from a comment on the second link:I found this
www.historyofwar.org/articles/weapons_spitfire_wings.html
The "e" wing was a further development of the Universal. It could carry either four 20mm cannon or two 20mm cannon and two 0.5in Browning machine guns. This time the cannon took the outer position and the machine guns the inner. This was partly because it gave more room for machine gun ammunition and partly because the bombs were carried below the inner gun positions, and there had been some problems reported when both cannon and bombs were on the same part of the wing. The "e" wing appeared in the second half of 1944.
And also this which has a lot of info difficult to quote
Sorting Out the "E" – American Armament for the Spitfire Mk. IX/XVI — Variants & Technology | Spitfire Mk. IX | Spitfire Mk. XVI
I think it was a Czech pilot that called it a pepperpot effect, with the spread of the guns and flexing of the wings when turning bullets flew everywhere, there are lots if interesting bits in there and other pages on the site.An interesting quote from a comment on the second link:
Another reason for the delay in the introduction of the XVI/low-back XIV was the reluctance of the Air Ministry to replace 4 x .303″ with 2 x .5″; it was found that, from the rear, the .5″ had no extra penetrative power over the .303″, and the general (lack of) shooting ability, by the average pilot, meant that the hosepipe effect of four guns, in a deflection shot, had a better chance of disabling the enemy pilot.
In 1938, Birkigt patented it and started production in their Geneva factory.
In 1938, an aircraft based version of the HS.404 was produced at the request of the French government.
(both sentences are from referenced from Chinn's book)
Steal the M-shell once captured and understood
This may be in error, at least it is contradicted by information in "Hispano Suiza in Aeronautics" by Manuel Lage. Initial patents date from Sept 1935 (in Belgium) , and development started earlier. The HS 404 had been "announced" it catalogs published by Hispano Suiza (in both French and Spanish) in late 1934. The gun did change considerably and new patents were granted, US patents were applied for in April of 1938.
I would be a little leery of the Oerlikon factory having 3 different cannon "in production" at this time. Samples yes, but production in terms of even dozens of guns per month? One reason Hispano Suiza licenced the Oerlikon and modified it to the HS 7 and HS 9 was that Oerlikon was chronically late in delivering guns for the French D 501-D 510 aircraft. ANd if the Oerlikons were "ready to go" why did both the French and Germans modify them?