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Since the Luftwaffe is now flying heavier bombers over Britain, how much earlier will the RAF get 20 mm guns into its Spitfires?
The trouble is you would still have a bloke standing behind the gun trying to calculate the lead and deflection angles of a Spit or Hurri flying in three dimensional space in the fractions of a second it took them to flash by while he himself is doing the same, the most likely outcome of fitting 20mm cannons in a 1940's bomber would be the gunners would miss with bigger bullets.
I totally agree with this plus the slower rate of fire and the gun being far more cumbersome to handle. In addition the arc of fire of a 20mm would be far less due to the much bigger bulk of the 20mm breach inside the very limited space inside the bomber. Reloading the gun would be a major issue as well as early war 20mm were drum fed.
You also have to remember that the long range escorts would be flying into a well organised and controlled integrated air defense network, worlds best at that time, you also have to contend with Dowding and Park, Park's organisation and tactic's during the BoB were exemplary and he poses a formidable opponent to any commander facing him. Giving the Bf 109 extra fuel to range over England with the bombers just exposes them to more intercepts from more fighter groups further from home with the same 9 seconds of 20mm ammunition. The RAF fighters on the other hand hit you crossing the channel coast, again inland over the target and a third time at the coast after they have landed and rearmed refueled, even relaying has them getting bounced at any point before they get on station. Bf 109's flying over England in 1940, likewise, Spitfires over France in 1941 faced a much different situation than P51's in late 1944-45.
How did that work in the He177, at least some of which had a 20 mm gun for the tail gunner?
Since the Luftwaffe is now flying heavier bombers over Britain, how much earlier will the RAF get 20 mm guns into its Spitfires?
A lot of times the discussions seem to assume the Germans would somehow have 1941-42 guns and mounts for their hypothetical 1940 4 engine bombers.
Germans fought the vast majority of the BoB with 7.9mm MG 15s with 75 round saddle drums and 20mm MG/FF or MG/FFM cannon with 15 or 30 round round drums in the flexible positions. The Ju 89 prototypes never got guns and the Do 19 might have had guns on the last aircraft (?) but descriptions paint a dismal picture. two man turret with one man controlling traverse and the other man controlling elevation.
The planes would have been little, if any faster, flown very little higher and not been a whole lot better armed than the twin engine planes. Hard to see any real advantage.
This is all quite true. But so is GrauGeist's point about the USAAF's experience. The defensive armament of a bomber, no matter how good, is not going to substitute good or better fighter cover.There is no evidence for that that, larger rounds are far less disturbed by air currents. The Ikara MG FF (basically the Oerlikon with the shorter medium velocity cartrige) weighed only 23kg and was successfully used on hand swivel mounts on a number of Luftwaffe aircraft as was the MG151/20. MG FF (and MG151) found themselves on swivel mounts on the nose of the He 111 and Do 217 and rear canopy of Ju 188.
The MG15 fired 1050 rpm of rifle calibre bullets from a 75 round magazine. A 4 second burst with say 5% hits would put about 4 rifle calibre rounds weighting 12.7 grams into a target.
The MG FF fired 540 rpm of 20mm bullets from a 60 round magazine. A 4 second burst with 5% hits would put about 2 x 20mm rounds weighing 134 grams in to the target.
If a 12.7 gram bullet hits a Hurricane bullet proof widescreen it gets scratched. If it hits an oil cooler or radiator the engine looses power 5-10 minutes latter.
If a 20mm bullet hits the windscreen the pilot dies or gets injured enough to make him loose interest. If it hits the shank of a propeller blade it gets blown of, if it hits the engine block it starts leaking oil and stops working.
Luftwaffe fighters sometimes had no more than 5 minutes over Britain and never more than 15 minutes. Drop tanks mean they turn up at high altitude near the UK coast with a full tank of internal fuel having used the jettison tank to form up, gain altitude, find the bombers they are escorting and cruise. The ammunition problem is over stated, 60 rounds at 540rpm is 11 seconds which still leaves plenty of (30-45) seconds of 7.92mm from accurate central guns. If you assume an Me 109E4 has an range of 400 miles its operational radius will be 1/3rd of that which is 133 miles. With a drop tank the range goes to around 650 miles and the operational radius goes to about 220-240 miles. The bombers are much safer, the Hurricanes and Spitfires take greater losses.
The 20mm MG FF was in service but the 40% faster firing higher velocity MG151/20 was not. The 20mm tail gun on the He 177 had about 55 degrees swing to either side if the tail gunner was in the prone position or about 30 degrees if he chose to sit. Glass looks optically clear, nice and flat and bullet proof.
The Hispano was not yet ready by the BoB and was particularly finicky in wing installations (OK in mosquito).
View attachment 581791View attachment 581792View attachment 581794
The rear gun on the He 177 was effective:
P-61 Black Widow vs. He 177 Greif (spoiler alert happy ending)
FalkeEins - the Luftwaffe blog: P-61 Black Widow vs. He 177 Greif
The proposed armament for the Do 19 and Ju 89 when they flew in 1936 on miserable 600hp engines was twin 20mm guns in the dorsal and ventral bathtub (presumably forward and rearward facing)
The MG FF and MG FFM could use 30,45,60,90 magazines and I think the 30 could come as a clip or drum. Choice of magazine seemed to depend on installation (nose, ventral bombola facing forward etc). I know the 90's were for the Fw 190 but pictures suggest both 30 and 60 were used on Luftwaffe aircraft in flexible mounts. It would depend on the space available.
"and not been a whole lot better armed than the twin engine planes" Yeah, sure, you are serious. A hit by a 134 gram 20mm bullet is likely to be devastating to a pilots bullet proof wind screen, engine block or propeller shank whereas a 12 gram 7.92mm round will likely do next to nothing other than a 20 minute repair. The rear guns, even if only a MG15 at least got a very clear shot at the approaching fighter and likely would have been a 20mm gun by 1939/40. Both the MG131 and MG81 were in production by 1940.
Nice example but the angle of fire with a drum loaded 20mm would be far less than an LMG plus the poor ballistics of the FF would significantly reduce the chances of a hit. I think you are also losing sight of the main aim of the bombers guns. The primary objective wasn't to shoot down the fighter, it was to stop the bomber being shot down. Your LMG hitting the windscreen would seriously craze it and almost certainly the fighter pilot would pull away, job done. It was very unusual to continue attacking a bomber once you have started to take hits.The MG15 fired 1050 rpm of rifle calibre bullets from a 75 round magazine. A 4 second burst with say 5% hits would put about 4 rifle calibre rounds weighting 12.7 grams into a target.
The MG FF fired 540 rpm of 20mm bullets from a 60 round magazine. A 4 second burst with 5% hits would put about 2 x 20mm rounds weighing 134 grams in to the target.
If a 12.7 gram bullet hits a Hurricane bullet proof widescreen it gets scratched. If it hits an oil cooler or radiator the engine looses power 5-10 minutes latter.
If a 20mm bullet hits the windscreen the pilot dies or gets injured enough to make him loose interest. If it hits the shank of a propeller blade it gets blown of, if it hits the engine block it starts leaking oil and stops working.
.
Maybe the fall of France took the LW by surprise as much as anyone, did anyone believe that they would be in a position to attack the UK in 1940 until they actually were.This is all quite true. But so is GrauGeist's point about the USAAF's experience. The defensive armament of a bomber, no matter how good, is not going to substitute good or better fighter cover.
The 4 engine bomber/higher altitude bomber/better armed bomber is misdirected resources in my opinion. The Germans would have been better off to just use 111's as they were. But develop more range into the 109, and better communication and tactics for escorting bombers. The easiest way to get the technological edge to win the BoB is improving fighter cover. Heavier bomb loads are great for strategic bombing, but Sealion (the feasibility of which is a whole seperation discussion) needed air superiority. The smaller two engine bombers were if anything, better suited to the tactical bombing requirements of the strategy. Flatten the airfields, then support the landing force as it crosses the channel, then support troops on the ground. Thus was right up the LW's alley as-equipped. But the air space was far too contested.
There is no evidence for that that, larger rounds are far less disturbed by air currents. The Ikara MG FF (basically the Oerlikon with theshorter mediumrealy short low velocity cartrige) weighed only 23kg and was successfully used on hand swivel mounts on a number of Luftwaffe aircraft as was the MG151/20. MG FF (and MG151) found themselves on swivel mounts on the nose of the He 111 and Do 217 and rear canopy of Ju 188.
Tony Williams says 11.5 grams for an AP bullet. Maybe he is wrong. Maybe 12.7 grams is for a lead cored bullet used in ground guns?The MG15 fired 1050 rpm of rifle calibre bullets from a 75 round magazine. A 4 second burst with say 5% hits would put about 4 rifle calibre rounds weighting 12.7 grams into a target.
The MG FF fired 540 rpm of 20mm bullets from a 60 round magazine. A 4 second burst with 5% hits would put about 2 x 20mm rounds weighing 134 grams in to the target.
No, 540rpm from a 60 round ammo supply is 6.66 seconds.The ammunition problem is over stated, 60 rounds at 540rpm is11 secondswhich still leaves plenty of (30-45) seconds of 7.92mm from accurate central guns.
Early He 177s used an MG 131 in tail with a smaller tail cone and no raised top for sitting position.The 20mm tail gun on the He 177 had about 55 degrees swing to either side if the tail gunner was in the prone position or about 30 degrees if he chose to sit. Glass looks optically clear, nice and flat and bullet proof.
The Hispano was not yet ready by the BoB and was particularly finicky in wing installations (OK inmosquitoBeaufighter).
The proposed armament for the Do 19 and Ju 89 when they flew in 1936 on miserable 600hp engines was twin 20mm guns in the dorsal and ventral bathtub (presumably forward and rearward facing)
"and not been a whole lot better armed than the twin engine planes" Yeah, sure, you are serious. A hit by a 134 gram 20mm bullet is likely to be devastating to a pilots bullet proof wind screen, engine block or propeller shank whereas a 12 gram 7.92mm round will likely do next to nothing other than a 20 minute repair. The rear guns, even if only a MG15 at least got a very clear shot at the approaching fighter and likely would have been a 20mm gun by 1939/40. Both the MG131 and MG81 were in production by 1940.
In terms of a hypothetical Ju 89 (and maybe Do 19) during the BoB there is no doubt that they would have been much tougher to bring down. Both these aircraft would have had a 20mm tail gun or two and caused considerably times more loses to the RAF fighters than the rifle calibre MG15 and MG81 on the He 111, Do 17Z and Ju 88A1. The rifle calibre guns had minimal effect and one imagines the MG131 had it been in service might have caused more harm and been more effective.
I don't much care what was proposed.
There is no evidence for that that, larger rounds are far less disturbed by air currents.
Luftwaffe fighters sometimes had no more than 5 minutes over Britain and never more than 15 minutes. Drop tanks mean they turn up at high altitude near the UK coast with a full tank of internal fuel having used the jettison tank to form up, gain altitude, find the bombers they are escorting and cruise. The ammunition problem is over stated, 60 rounds at 540rpm is 11 seconds which still leaves plenty of (30-45) seconds of 7.92mm from accurate central guns. If you assume an Me 109E4 has an range of 400 miles its operational radius will be 1/3rd of that which is 133 miles. With a drop tank the range goes to around 650 miles and the operational radius goes to about 220-240 miles. The bombers are much safer, the Hurricanes and Spitfires take greater losses.
I suggest you take a ride in a Cessna 172 and once leveled off and cruising, open the windscreen and hold a broomstick out about three feet and try and hold it steady.It has nothing to do with air currents and everything to do with trying to hit something flashing by you doing hundreds of miles an hour
I suggest you take a ride in a Cessna 172 and once leveled off and cruising, open the windscreen and hold a broomstick out about three feet and try and hold it steady.
When you've mastered that, come back and let us know how that worked out.
It has nothing to do with air currents and everything to do with trying to hit something flashing by you doing hundreds of miles an hour.
I don't think anyone was debating that point. More that the effects of wind on trajectory and other nuances are moot when precision-aim simply isn't happening/possible.I was too busy to read the entire convo, so my apologies if I missed something or the context of this post. But wind does affect the trajectory of a bullet, ANY bullet, and any size round, just as it does to any flying object. It is simple physics and aerodynamics. Some call it Wind Drift.
3.2 Effects of Winds - Sierra Bullets
I don't think anyone was debating that point. More that the effects of wind on trajectory and other nuances are moot when precision-aim simply isn't happening/possible.
I think it could be conceded that an attacked making a direct and steady tail-on approach would give an opportunity for a marksman but pilots favouring this method probably wouldn't last long between tailgunners and escort fighters. But that's only my 2 cents.
Of course wind currents will have an effect on the trajectory of a bullet (or cannon shell) in flight.I think the argument was the projectiles were disturbed by air currents, not the gun barrels?, by your example a bigger 20mm barrel would be harder to train than a thinner shorter .303/7.92mm so the gunners would be further disadvantaged using bigger guns.
I thought that the whole idea of a turret was to have the guns securely mounted and smoothly traversed. When you see footage of waist gunners in B-17s with the movement of the plane, gun and gunner plus the recoil, the effect is that he is just firing bullets in a general direction.
The trouble is you would still have a bloke standing behind the gun trying to calculate the lead and deflection angles of a Spit or Hurri flying in three dimensional space in the fractions of a second it took them to flash by while he himself is doing the same, the most likely outcome of fitting 20mm cannons in a 1940's bomber would be the gunners would miss with bigger bullets.