What was the most effective naval anti-aircraft gun of WW2?

[Bgile]

I think about the same. A battleship at anchor can be hit by determined bomber crews, and it really only takes one hit from a bomb of that type to wreck the ship. Depending on what version of FC equipment the ship had, bombers might have been lost, but I still think it's likely the ship would have been hit. Fighter interception is really what was needed and apparently the German fighter command dropped the ball that day.

Also, I believe Tirpitz wasn't relying only on her own AA fire. Weren't there quite a few fixed installations as well?

[tommy303]

A question that has sometimes puzzled me is why the KM30 37 mm were never replaced on the Scharnhorst and Gneisenau by the faster firing 42 or 43 models as in cruisers and destroyers.

It would certainly have been frustrating to ship commanders and crews not to have the latest automatic 3,7cm Flak guns and have to rely on the older manual loaded 3,7cm Flak SK/C30. However, the problem was one of production and priorities. The Luftwaffe and Army had higher priority than the Kriegsmarine, which is understandable considering the Kriegsmarine's big ships were usually in port rather than on the front line like the ground troops, air crews and air bases, and Flak defences for the fatherland. Within the Kriegsmarine, U-boats, MTBs and destroyers had higher priorities due to their higher levels of activity. The introduction of the 42 and 43 models in sufficient numbers simply came too late for Scharnhorst and Tirpitz. Had the two ships survived longer than they did, they would probably have received the new weapons, or like the Prinz Eugen and Hipper, received the 4cm Bofors. The Bofors was the Norwegian produced version of the Swedish design and both the gun and ammunition were in limited production under German occupation. That Prinz Eugen and Hipper received the 4cm with all the attendant problems associated with spares and ammunition (being non-standard in the German arsenal), may be indicative of how hard a time German armaments industries, in particularl Rheinmetall-Borsig, were having meeting the demand.

[RobertsonN]

Thanks for information about the 'German' 40 mm. I had been under the impression the Germans used captured Polish weapons. I have read elsewhere that the Germans also purchased Oerlikons from Switzerland during the War.
As far as supplementary AA on the final attack, it is likely that the two 'AA cruisers', old Norwegian ships on which the Germans had mounted six of the smaller type 4.1 in guns with elevation up to 70 deg, were still with the Tirpitz. There may have been shore fire as well. So the total number of shells fired was probably well over the number I estimated. A look at the Bomber Command War Diary site shows that no aircraft were lost over the target on any of the three Tallboy raids. However, on each of the last two raids one Lancaster was badly damaged by Flak and forced to land in Sweden. These planes would be counted as losses. So there were minimal losses even though no planes were shot down. No doubt you will have seen the excellent US Newsreel films (5 in number) about the attacks on the Tirpitz. That the RAF modified Lancasters (with different engines) for the last two raids and that there was one Lancater per Tallboy raid that had just a film team on it shows that the Tirpitz, whatever its military value by then, was still a prestige target.
Some sites, in discussions about Japanese aircraft suggest that because they did not have self-sealing fuel tanks that they more easily caught fire and were lost. Was it the US experience that it was easier to shoot down aircraft in the Pacific as opposed to the European theatre?

[Bgile]

Some sites, in discussions about Japanese aircraft suggest that because they did not have self-sealing fuel tanks that they more easily caught fire and were lost. Was it the US experience that it was easier to shoot down aircraft in the Pacific as opposed to the European theatre?

That has been my impression. For much of the war Japanese aircraft lacked self sealing fuel tanks and armor.

[tommy303]

I have read elsewhere that the Germans also purchased Oerlikons from Switzerland during the War.

Yes. The two main purchasers of the Oerlikon were the Army and the Luftwaffe. Army designation was Flak 28 or 29, while the Luftwaffe purchased theirs for aircraft armament under the designation 2cm MG/FF. Once the Army had sufficient numbers of 2cm Flak 38s on hand, they handed their stocks of Oerlikons over to the Navy which used them on a number of small vessels, but not apparently on any of the major warships. This is understandable, as the 2cm ammunition used in the Oerlikon was not interchangeable with ammunition for the Flak 30 and Flak 38.

[delcyros]

I wonder how these shells maintained structural integrity against the accelerations required for such high MVs?

In all applications I know of for the M-Geschoss they never cut down the mv. Rather contrary, in smaller guns (f.e.20mm and 30mm range) the adoption of the M-Geschoss, which was a bit lighter than a normal HEI/HET-thanks to different density figures for high explosive and steel, respectively- significantly increased the muzzle velocity. Still, the sectional density was lower, hence a poorer ballistic coefficient and worse energy retention of these rounds.
Downrange striking velocity wasn´t considered as important as blast effect againt aircraft targets.

But I am not very enthusiastic about the reliability of these rounds structurally. Probably not a problem during firing these weapons (no such safety records to the best of my knowledge) but what RobertsonN meantioned above as "berstfrei" represents a dud by impacting strong surfaces. They would also desintigrate hitting armourplates in airplanes with greatly reduced effect.

I was also wondering why the US didn´t adopt the M-round for it´s light AAA in the Pacific (and else). I understand that the principle was adopted in the 50´s and 60´s, though.

[Bgile]

Maybe it was too difficult to manufacture in the required quantities.

[tommy303]

Or required too much specialized equipment to draw and temper the shells, while there were any number of machine shops that could make the normal HE cannon shell.

[RobertsonN]

Delycros above says that the old semiautomatic 37 mm used M-Geschoss since 1941. Did the Bismarck have these later rounds? Also did the muzzle velocity usually given for these weapons of 1000 m/s apply to this round or an earlier one. Perhaps the point about the poorer energy retention of these rounds explains why the 37 mm had a significantly lower range than the Bofors despite having a higher muzzle velocity, a point that has always puzzled me. The Germans did occasionally adopt the practice of adopting a new 'higher technology' round for an obsolescent weapon to make it competitive again or as a stop gap measure. For example, the 5 cm antitank gun was outclassed by Russian T34s, the Germans reacted by adopting tungsten cored rounds which slowed down less with increasing range due to their greater inertia. The infamous depleted uranium rounds of our own day would appear to be following the same idea. The 37 mm M-Geschoss had about 5.3 times the explosive charge of a Bofors round (does anything know what the pompom burster was?). So with an rof of 30 rpm it could put about the same amount of high explosive into the sky as a Bofors at 120 to 160 rpm (but still with a much lower chance of hitting the target). The 20 mm M-Geschoss burster was about 3.5 times that of the Oerlikon and a little over half that of the Bofors. Perhaps the kill probability of the German 20 mm was significantly higher than that of the Oerlikon, which was always regarded as unsatisfactory.The berstfrei results I mentioned earlier were of 15 and 20.3 cm noze fuzed HE shells striking 15 to 30 mm plate depending on distance. Aircraft armor would likely have had the same effect on M-Geschoss. Here again it was a trade-off: the RAF went for high bomb load/low armor, the USAF heavier armor, lower bomb load.
This was at the cost of more expensive manufacture and the use of alloys which might have been put to better use elsewhere and of course the Germans were struggling with Ersatz steels throughout the war (all steam engine boilers built after the late 1930s had to be replaced in the 1950s because of safety/high maintenance concerns).

[Neoconshooter]

It matters little what type of gun is used, it IS the fire control system that makes the big difference!
Search for pictures of 20 MM guns. Some have huge bulky sighting systems and other have a ring and bead. Look at 40 mm quads, some have radar dishes and others do not. Which type do you think will be more effective. You see it is the stuff you can not see, or do not notice, like the large boxes housing FC Computers beside, or behind the mounts that makes the largest differences.
The second most important ingredient in the mix is the type of ammo used. Proximity fused shell from larger caliber cannon are the clear winners here, far out pacing any other munition. The larger gun with the highest rate of fire easily out ranges the smaller and each has a band where it will be most effective. The farther out you engage the enemy, the least likely he is able to damage you.

So, to summarize, 5/38 Caliber gun, with either on mount, or remote mount Radar and FC Computer, shooting proximity fused ammo is the king of WW-II guns.

While the British invented the computer controlled firing predictor, it was the Americans who perfected it in mid/late WW-II to the point it could be used to shoot down aircraft. Regardless of tech sharing, no other nation or Navy implemented such a system during the war.

[Neoconshooter]

I think about the same. A battleship at anchor can be hit by determined bomber crews, and it really only takes one hit from a bomb of that type to wreck the ship. Depending on what version of FC equipment the ship had, bombers might have been lost, but I still think it's likely the ship would have been hit. Fighter interception is really what was needed and apparently the German fighter command dropped the ball that day.

Also, I believe Tirpitz wasn't relying only on her own AA fire. Weren't there quite a few fixed installations as well?

IIRC, they dropped 18-19 Tallboys and got one hit and 1-2 near misses? One of the bombs landed over a mile away, again IIRC. If only those three planes would have been shot down, the Tirpitz would have been unscathed?
The ability of Radar directed medium caliber guns shooting proximity fused shell at target less than 20,000'/6,096M during WW-II is very well documented earlier in this very thread. The possibility that such a system could have saved Tirpitz is beyond question

[dunmunro]

It matters little what type of gun is used, it IS the fire control system that makes the big difference!
Search for pictures of 20 MM guns. Some have huge bulky sighting systems and other have a ring and bead. Look at 40 mm quads, some have radar dishes and others do not. Which type do you think will be more effective. You see it is the stuff you can not see, or do not notice, like the large boxes housing FC Computers beside, or behind the mounts that makes the largest differences.
The second most important ingredient in the mix is the type of ammo used. Proximity fused shell from larger caliber cannon are the clear winners here, far out pacing any other munition. The larger gun with the highest rate of fire easily out ranges the smaller and each has a band where it will be most effective. The farther out you engage the enemy, the least likely he is able to damage you.

So, to summarize, 5/38 Calibre gun, with either on mount, or remote mount Radar and FC Computer, shooting proximity fused ammo is the king of WW-II guns.

While the British invented the computer controlled firing predictor, it was the Americans who perfected it in mid/late WW-II to the point it could be used to shoot down aircraft. Regardless of tech sharing, no other nation or Navy implemented such a system during the war.

All the major navies had AA FC systems that could shoot down aircraft. The introduction of radar ranging by the RN in 1939/40 radically improved the effectiveness of AA systems against straight line targets but no WW2 era long range AAFC system could reliably shoot down manoeuvring aircraft, except at close range, with VT ammo, when the ToF became very short.

[Dave Saxton]

IIRC, they dropped 18-19 Tallboys and got one hit and 1-2 near misses? One of the bombs landed over a mile away, again IIRC. If only those three planes would have been shot down, the Tirpitz would have been unscathed?
The ability of Radar directed medium caliber guns shooting proximity fused shell at target less than 20,000'/6,096M during WW-II is very well documented earlier in this very thread. The possibility that such a system could have saved Tirpitz is beyond question

It matters little what type of gun is used, it IS the fire control system that makes the big difference!

Tirpitz had a Wuerzburg mounted to a M42 director and firecontrol system.

[alecsandros]

IIRC, they dropped 18-19 Tallboys and got one hit and 1-2 near misses? One of the bombs landed over a mile away, again IIRC. If only those three planes would have been shot down, the Tirpitz would have been unscathed?
The ability of Radar directed medium caliber guns shooting proximity fused shell at target less than 20,000'/6,096M during WW-II is very well documented earlier in this very thread. The possibility that such a system could have saved Tirpitz is beyond question

It matters little what type of gun is used, it IS the fire control system that makes the big difference!

Tirpitz had a Wuerzburg mounted to a M42 director and firecontrol system.

But hiting the Lancasters at 7km altitude was a very difficult task...

[Thorsten Wahl]

one has to consider that Tirpitz Air defense was range limited by surroundig mountains. So it was somwhat difficult to capture, track and attack aircraft at greater distances.
Additional a great number of fighters directly attack flak Crews and AA-directors parallel to the main attack and cause considerable casualities to the Flak- crews. These aircraft often use "bush hopping" on the approach.

The british combined main air attacks of high level and low level bombing attacks from different directions together with strafing attacks of the fighters against Tirpitz wich usually last for less then two minutes.