Defensive armament

Schweik said:

Worst 13mm or lowest velocity 20mm can still easily shoot down a 1940 fighter with a single hit, definitely with 3 or 4.

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Without a doubt, if you can get that hit before you run out of ammunition.

Schweik said:

Worst 13mm or lowest velocity 20mm can still easily shoot down a 1940 fighter with a single hit, definitely with 3 or 4.

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Bad argument.
A 1940 fighter could be shot down with a single 7.63-7.9mm hit also.
If you are depending on a handful of hit's from either the rcmgs or from a 12.7-13mm machine gun you are depending on a lot of luck in the placement of the hits.

The German 13mm round had about 55 percent of the kinetic energy of the US .50 cal at the muzzle and since the bullet was poorer in shape and lighter it lost velocity quicker meaning at striking distance it was under 1/2 as powerful.
It is possible to shoot down /a 1940 fighter with a single hit it but it is not likely, not even with 3 or 4. How many Japanese fighters did the Americans shoot down with just 3-4 hits?

The thing is, with a bombers defensive armament, especially a tail, dorsal or ventral gun, it is basically there to punish the foolish fighter pilot who comes up from behind. It's there to keep them honest so they don't try it, but inevitably some do. An attack from behind generally means a slower approach and also that that the front of the aircraft is presented to the gunner. That is optimal for the gunner. If the defensive armament effectively outranges the guns on the fighter it's even better, that means they'll have a longer time to aim and get a hit. My understanding is that especially with a lot of these early guns, the ideal was to shoot short bursts, 4 or 5 rounds at a time.

If a fighter is coming up behind a bomber, there is a fairly good chance of being hit in the engine or the radiator or the windscreen / cockpit. I say this because I know it happened to quite a few, maybe most of the fighter pilots whose biographies I have read at one point or another in their career. The result was often a disabled aircraft and / or a wounded pilot. Saburo Sakai is a famous example of this, though he claims he misidentified the plane he was attacking and was taken by surprise.

So yeah I would say, a 13mm HMG gun, or a 20mm cannon like on the Betty, could be quite devastating to an attacking fighter. A single hit can disable an engine or kill or wound a pilot. The same is also true of a .30 caliber defensive weapon in theory, especially if mounted in a power turret in a multiple-gun position, but against the lighter weapon an attacking fighter with 12.7mm or 20mm guns can shoot first, often by quite a bit. If their aim is good (big if) they have the advantage.

Schweik said:

If the Sleaford Mods variant saw action the Germans would have been on the run.

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To be fair the Sleaford Mods scare a lot of people

Shortround6 said:

Bad argument.
A 1940 fighter could be shot down with a single 7.63-7.9mm hit also.
If you are depending on a handful of hit's from either the rcmgs or from a 12.7-13mm machine gun you are depending on a lot of luck in the placement of the hits.

The German 13mm round had about 55 percent of the kinetic energy of the US .50 cal at the muzzle and since the bullet was poorer in shape and lighter it lost velocity quicker meaning at striking distance it was under 1/2 as powerful.
It is possible to shoot down /a 1940 fighter with a single hit it but it is not likely, not even with 3 or 4. How many Japanese fighters did the Americans shoot down with just 3-4 hits?

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By the same token, actually hitting a He111 with a single bullet from a Hurricane would need a special kind of marksmanship.

fastmongrel said:

To be fair the Sleaford Mods scare a lot of people

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They would crush any SS unit with sheer contempt!

pbehn said:

By the same token, actually hitting a He111 with a single bullet from a Hurricane would need a special kind of marksmanship.

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On the Hurri and Spit, you also had an unprotected fuel tank right in front of the cockpit, right? That was another major vulnerability in attacking bombers in particular.

Schweik said:

On the Hurri and Spit, you also had an unprotected fuel tank right in front of the cockpit, right? That was another major vulnerability in attacking bombers in particular.

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Not really, its behind the engine. A BoB pilot (Wellum I think) said he felt completely safe attacking a bomber they only has rifle calibre MGs and he was behind an engine and BP glass. You may take a few hits that could eventually force you to land or even bale out but it was over UK land so very little risk to the pilot.

I would think in particular it would make the ventral attack (from below and behind) a bit riskier. I have read of those catching fire even in Spit V in the Med. Agreed less risk if it's a rifle caliber defensive gun.

Schweik said:

I would think in particular it would make the ventral attack (from below and behind) a bit riskier. I have read of those catching fire even in Spit V in the Med. Agreed less risk if it's a rifle caliber defensive gun.

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The Spitfires tanks were self sealing that isn't proof against catching fire just lessens the risk. Some pilots prefered a ventral attack in the BoB. The ventral guns on a German bomber were hard to operate.

pbehn said:

Not really, its behind the engine. A BoB pilot (Wellum I think) said he felt completely safe attacking a bomber they only has rifle calibre MGs and he was behind an engine and BP glass. You may take a few hits that could eventually force you to land or even bale out but it was over UK land so very little risk to the pilot.

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One book (iirc, it was The Hardest Day) had an interviewed pilot saying he would press an attack regardless of gunners, as he had 8 guns to the gunner's one.

Schweik said:

Yes, a lot of the early German bombers also had the problem that most of the crew were concentrated in a small area, so a machine gun burst or a single AAA or air to air cannon shell hitting in the right place (like in the nose gondola / cockpit of a Ju 88 or Do 17) the whole crew could be killed. There was some value in having redundant guns for a single gunner, if only because jams and stoppages were so common with all types of machine guns especially on aircraft.

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You tend to find a lot of armour in the German bombers to protect the crew, this includes bullet proof glass. This includes bulkhead armour for the entire crew and full seat armour for the pilot, contrasting with the legendary Lancaster's Armour which was limited to the head rest of the pilot. Of course the main crew member to protect was the pilot since without him the rest of the crew would be lost.

Below Ju 88A4/A5


Below Ju 188
[/QUOTE][/QUOTE]

The Lancaster had a bit more than that. Armour plate was also fitted to:

Also deflector plates around the mid-upper turret and over the engines.

Shortround6 said:

Bad argument.
A 1940 fighter could be shot down with a single 7.63-7.9mm hit also.
If you are depending on a handful of hit's from either the rcmgs or from a 12.7-13mm machine gun you are depending on a lot of luck in the placement of the hits.

The German 13mm round had about 55 percent of the kinetic energy of the US .50 cal at the muzzle and since the bullet was poorer in shape and lighter it lost velocity quicker meaning at striking distance it was under 1/2 as powerful.
It is possible to shoot down /a 1940 fighter with a single hit it but it is not likely, not even with 3 or 4. How many Japanese fighters did the Americans shoot down with just 3-4 hits?

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The MG131 however had a rate of fire of 900 RPM compared to the M2H2 WW2 Browning's rof of 450 RPM-550RPM, so destructive power, penetration aside, might be about the same within range. The MG131 also could fire an effective explosive round. A single MG131 would be at least as destructive as the two 0.303 Browning on a RAF dorsal turret. The Low drag electric turret used on various Luftwaffe bombers had a niche in terms of cost in weight, fire power and low drag. Lancaster's and other British bombers often operated without the dorsal turret due to its extraordinary weight and drag, they might have done well with something similar.

There really wasn't much choice for the Luftwaffe.

Allied medium bombers such as the B25 (CW R-2600 1700hp), B-26 (PW R-2800 1850-2000hp) and wellington (Hercules 1500-1800hp) could afford the drag of a large dorsal turret and tail turret. Without that level of power turrets were impractical on German twin engine designs. The BMW 801D was in very short supply and often forced to operate at reduced boost to allow use of 87 octane B4 fuel. It was needed for the Fw 190 fighter and small numbers for Ju 88R and Ju 88G night fighters.

When powerful turrets appeared on Luftwaffe bombers they were 20mm guns and showed up on 4 engine aircraft: Fw 200C3, Ju 290 and various Blohm and Voss flying boats.

The Me 210 was intended to replace the Ju 87, Me 110 and Ju 88. This would have allowed shutdown both the Me 110 line and the He 111 line with the Ju 88 taking over the longer ranged roles of the He 111.

It's worth considering what might have been possible if the Jumo 211J had preceded down the route of use of C3 fuel.

The He 111 and Me 110 lines were in the process of running down when the Me 210 had to be cancelled. This forced a restart of the He 111. The Development of the He 111 had thus been neglected.

On top of that is that the Ju 288 and He 177 bombers, also replacements for the He 111 had also succumbed to engine delays.

The aircraft version of the Browning M2 was about 800 rounds/min.

'Effective' 13-mm HE round depends on who you're asking, I guess. After testing the British were never impressed with any of the axis machine gun HE rounds. That said in my opinion they would have a reasonable psychological value and their effects (if not destructive) would serve a defensive gun well.

"Lancaster's and other British bombers often operated without the dorsal turret due to its extraordinary weight and drag..." I think it would be more accurate to say they operated without the dorsal turret for a handful of special missions.

EDIT: for what it's worth -- general British calculations on the cost of a 2 x .303 mid-upper turret:

The ventral turret was the one regularly left behind.

swampyankee said:

One book (iirc, it was The Hardest Day) had an interviewed pilot saying he would press an attack regardless of gunners, as he had 8 guns to the gunner's one.

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When you look at the position of a He111 front gunner its hardly a fair fight.