Yet another .50 vs 20mm thead.

[davebender]

Hs.404 cannon may have been durable but it wasn't known for reliability during combat.

 

[Shortround6]

Hs.404 cannon may have been durable but it wasn't known for reliability during combat.

That may be hard to judge. We have the figures for the .50 cal machine gun, which had a fair share of trouble in some early installations, But figures for a number of other guns seem to hard to come by. We know that British Hispanos had a lot pf trouble in early Spitfires but does anybody have figures for the Hurricane II, Whirlwind, Beaufighter at about the same time?

What was the mean time between failures or malfuctions for other 20mm cannon ?

 

[buffnut453]

By "some early installations" you mean pretty much every fighter installation thru late 1942. We often forget, given the 50 cal's outstanding performance in later P-47s, F4Us, F6Fs and P-51Ds, that the gun had major issues as installed in the F4F, P-40, Buffalo and P-51B that continued throughout most of 1942.

 

[CobberKane]

That may be hard to judge. We have the figures for the .50 cal machine gun, which had a fair share of trouble in some early installations, But figures for a number of other guns seem to hard to come by. We know that British Hispanos had a lot pf trouble in early Spitfires but does anybody have figures for the Hurricane II, Whirlwind, Beaufighter at about the same time?

What was the mean time between failures or malfuctions for other 20mm cannon ?

From memory, there is an exhibit in the RNZAF museum that states the Hispano averaged one stoppage per 600 rounds, but this increase significanlt in dusty conditions

 

[Jabberwocky]

From memory, there is an exhibit in the RNZAF museum that states the Hispano averaged one stoppage per 600 rounds, but this increase significanlt in dusty conditions

Average stoppage rates for Hispano cannon varied wildly with local conditions, aircraft types and installation and feed mechanism used.

2TAF stoppage rates for 1944/1945 were about 1 every 1560 rounds, with about 50% of stoppages due to belting/feed mechanism problems. Fighter Command stoppage rates in 1942 and 1943 were about 1 in 1800-2000 rounds, thanks mostly to the better servicing facilities and less dust in the mechanisms. I've also seen references to Hispano stoppage rates in the UK of about 1 per 3000, but no indication of what aircraft or what period.

Stoppage rates were generally highest in early Spitfire Mk Vs, particularly with the 60 round drum magazine and before several gun heating mods were made. The Mk IX onwards had much better cannon reliability. Beaufighter and Mosquito armaments were also reputedly quite reliable. One RAAF crew sped their Hispano Mk IIs on a Beaufighter up to 1000-1100 rpm with no ill effects reported.

The RAAF found stoppage rates that were ridiculously high (more than 1 in 250 rounds if I remember Darwin Spitfires correctly) when fighting over Darwin. A combination of the dry, dusty conditions and very high altitudes of combat, along with poor ammunition and incorrectly installed (or non-existant) cannon heating due to the hodepodge of Spitfires they got. The Austin feed mechanisms - which were badly bodged when the company took over some work from Molins - were also heavily to blame. The British Small Arms feeds were also horrible, and Molins ended up doing a re-design the feed mechanism (shaving five pounds of the original wight in the process).

The RAF also had problems with stoppage rates in Malta as well. Again, ammunition was a problem, along with dust. One account has toilet paper being laid over the breech mechanism to keep it from collecting dust while Spitfires were taxiiing on dirt runways.

The Hispano Mk V was reportedly more reliable than the Mk II. I think the Mk V went with a new feed mechanism (maybe another Molins design) that helped sort some of the problems out. The life of most of the smaller parts in a Hispano Mk V was only 2500-3000 rounds, so this would be roughly the upper limit for stoppage rates, I'd suggest.

 

[tomo pauk]

Thanks, not an everyday stuff to read about.

 

[davebender]

The U.S.A.F. Armaments Laboratory concluded the Hs.404 cannon wasn't very reliable. I'm not going to dispute their expert opinion.

 

[wuzak]

The U.S.A.F. Armaments Laboratory concluded the Hs.404 cannon wasn't very reliable. I'm not going to dispute their expert opinion.

But was that he British built one or the US manufactured one?

I think there is little doubt that the US manufactured Hispano was less reliable than the British built one.

 

[Jabberwocky]

But was that he British built one or the US manufactured one?

I think there is little doubt that the US manufactured Hispano was less reliable than the British built one.

US Hispano reliability was anywhere from 1/3rd to 1/8th of Hispanos of UK manufacture. Early ground tests saw the reliability as low as 1 stoppage every 30-60 rounds.

The major problems were the chamber length being 1/16th of an inch too long, resulting in lightly struck percussion caps, and belt mis-feeds.

By 1944 the US Hispano was experiencing 1 stoppage every 505 rounds in the P-38's nose mount (8th AF, in combat). By the end of the year reliability was about the same as in the RAF - roughly 1 stoppage every 1600 rounds. I believe this was mostly because of the lower altitudes combat was taking place at through the second half of the year.

 

[CobberKane]

US Hispano reliability was anywhere from 1/3rd to 1/8th of Hispanos of UK manufacture. Early ground tests saw the reliability as low as 1 stoppage every 30-60 rounds.

The major problems were the chamber length being 1/16th of an inch too long, resulting in lightly struck percussion caps, and belt mis-feeds.

By 1944 the US Hispano was experiencing 1 stoppage every 505 rounds in the P-38's nose mount (8th AF, in combat). By the end of the year reliability was about the same as in the RAF - roughly 1 stoppage every 1600 rounds. I believe this was mostly because of the lower altitudes combat was taking place at through the second half of the year.

Both your posts make me wonder whether the RNZAF were using US or UK Hispanos and under what condidtions (though I believe the Kiwis did most of their work in places like PNG and the pacific - pretty basic). Come to think of it, I can't think of a single RNZAF aircraft that use cannon anyway. Don't take too much from museum exhibits, I suppose

 

[Jabberwocky]

Both your posts make me wonder whether the RNZAF were using US or UK Hispanos and under what condidtions (though I believe the Kiwis did most of their work in places like PNG and the pacific - pretty basic). Come to think of it, I can't think of a single RNZAF aircraft that use cannon anyway. Don't take too much from museum exhibits, I suppose

RNZAF aircraft in the Pacific were almost exclusively US supplied.

However, there were six New Zealand squadrons in service in Europe and the Middle East with various commands (RAF and Coastal Command), and they operated a mix of Beaufighters and Mosquitos.

The cannon installation in the early Beaufighters was pretty prone to stoppages, probably because it used the 60 round drum magazines. Fortunately, the navigator could be called on to clear jams, as the cannon were accessible from the cockpit. He was also responsible for reloading the cannon in flight, which I can't imagine would have been pleasant.

Later the Beaufighter got belt feed for the cannon, complete with a foot operated pneumatic cocking device.

 

[CobberKane]

RNZAF aircraft in the Pacific were almost exclusively US supplied.

However, there were six New Zealand squadrons in service in Europe and the Middle East with various commands (RAF and Coastal Command), and they operated a mix of Beaufighters and Mosquitos.

The cannon installation in the early Beaufighters was pretty prone to stoppages, probably because it used the 60 round drum magazines. Fortunately, the navigator could be called on to clear jams, as the cannon were accessible from the cockpit. He was also responsible for reloading the cannon in flight, which I can't imagine would have been pleasant.

Later the Beaufighter got belt feed for the cannon, complete with a foot operated pneumatic cocking device.

New Zealand squadrons also flew Tempests, and I think Typhoons, in the ETO. But yes, all the aircraft that bore the NZ insignia were in the PTO I believe and sourced from the USA; Buffalos and P40s and Hudsons to start with, then Corsairs later.
Interstinggly, I believe the first aiar to air kill of the RNZAF was scored by a gunner in a Hudson. He was Moari, which maybe gives some indication on how far ahead of the curve New Zealand was in terms of racial inclusiveness at the time.

 

[fastmongrel]

He was Moari, which maybe gives some indication on how far ahead of the curve New Zealand was in terms of racial inclusiveness at the time.

I think George Nepia might have had something to say about that. NZ was ahead of the curve but not by much.

 

[CobberKane]

I think George Nepia might have had something to say about that. NZ was ahead of the curve but not by much.

By a lot, I think - compared to the situations in the USA and Australia at the time - but still with a hell of a lot of work to do, for sure.
Incientally, I coudn't find the reference to the kill when i looked for it again, so don't take it as gospel.

 

[Glider]

The RAF also had problems with stoppage rates in Malta as well. Again, ammunition was a problem, along with dust. One account has toilet paper being laid over the breech mechanism to keep it from collecting dust while Spitfires were taxiiing on dirt runways.

In The Spitfire Year 1942 which recounts the fighting over Malta, they did have stoppage problems with the 20mm but it was traced to US manufactured ammunition. Despite the serious shortages on Malta they destroyed all the US ammunition and the problem stopped

 

[Edgar Brooks]

As so often, fighter pilots were completely in the dark, when it came to decisions made by the Air Ministry; today, it tends to be forgotten that the RAF always had to consider the possibility of a continuation of the Battle of Britain, with its concentration on killing bombers, not just fighters. The following is a matter of records, so, please, curb any tendency to leap up and down, crying, "That's rot." (or worse.)
It was found that the .5" was no better at penetrating German bomber armour than the .303", and, with the average pilot unable to properly master the art of deflection shooting, it was decided that four fast-firing .303" guns were more likely to fatally hit (or at least immobilise) the crew, from the side, than a pair of slower-firing .5". The 20mm was also considered essential, if, as feared, Germany produced bigger, more capable, and better-armoured, bombers. I'm not sure where the idea, that a Spitfire wing was not designed to carry 4 x .303" Brownings, comes from, since it was always designed with that armament, with the elliptical shape ensuring that the guns could be fitted into such a slim wing.
The .5" armament, in U.S. aircraft, made more sense, since their opponents were, most often, fighters, not bombers.
The 20mm was already being planned for (and tested) before the war started, but ammunition feed troubles bedevilled the system; at least five companies tried to come up with a workable system, with Chatellerault just edging out Molins (who were instrumental with the Mosquito "Tsetse.") Eventually the Vc was capable of doing what the Air Ministry wanted.
Leigh-Mallory did his utmost to get the .5" accepted, but was continually told to "push off" by the Air Ministry, until (and it's a major moment) the gyro gunsight made its appearance in 1944; almost overnight, average pilots could hit their targets, so the Ministry finally relented, and allowed the .5" to be fitted into Spitfire IXs, XIVs, and (post-war) XVIIIs (almost too late, since the soon-to-arrive 21, and Tempest, used 4 x 20mm cannon, and no machine guns at all.)
Edgar

 

[Shortround6]

To add to this the .50 cal gun/s and ammo tested by the British in the 1930s were not the .50 cal guns and ammo of 1942 or of 1944. And the guns/ammo of the Korean war were yet again different.

The 1930s guns fired at 600rpm (at best) and were down to 400-500rpm when synchronized. The ammo used a slightly heavier bullet ( enough to win bar bets but that is about it) but operated at a lower pressure and had a velocity closer to 2500fps than 2900fps. I am not sure when the high velocity AP rounds showed up. The long pointy nose that helped the bullet retain velocity very well also meant that it tipped easier when penetrating aircraft skin and so it had a greater tendency to it interior barriers (like internal armor) sideways which hurt penetration. The 1942 belts were about 40% AP, 40% incendiary and 20% tracer fired from the 750-850rpm guns (which came in at some point in 1940). The 1944 belts were 90-100% M8 API ammo.

The British changed the ammo types used in the .303 guns too. BoB used about 3 guns firing ball ammo. Two with AP, two with MK IV incendiary tracer and just one with the MK VI (De Wilde) ammo. Later on there were different mixes for different uses and for different aircraft. As the De Wilde became more available it was used in ever increasing amounts. Ball ammo disappeared soon after the BoB.

 

[tomo pauk]

Those .5" guns/ammo: was it the Vickers type, or Browning?

 

[Shortround6]

It was the Browning. The .50 cal Browning dates back to the early 20s (work started during WW I). Powder and ballistics of a number cartridges improved during that time. By 1938 or so the American 30-06 could move a bullet (150 grains) as fast using 42,000lbs chamber pressure as it took 50,000lbs pressure in 1906. That is peak pressure, the longer burning "newer" powder/s had a bigger area under the pressure curve even if the peak was lower. move the peak back up and you could use heavier bullets or get more velocity.

 

[fastmongrel]

Did the Air Ministry test any other 0.5" guns I am thinking particulary of the FN 13.2 it seems to have been lighter, fired HE round with more explosive and had a higher ROF. Though thems internet facts and not to be taken as 100% true