Tank busting Stuka gun

[Vinnie]

What would be the rating of the gun mounted on the Stuka at Kursk? Would it be a 37L or 37LL?
MY gut feeling is that it shoulkd be the LL version but I note the German Chapter H has no LL versiions of the 37 mm gun.

 

[Paul M. Weir]

The gun was an adoption of the 37mm FlaK 18 as the BK 3.7 firing APCR (https://en.wikipedia.org/wiki/BK_3,7). So use the 37L APCR values. Given the ability of the Ju-87 to enter a steep dive you might allow a point attack from an adjacent hex as per E7.403. While an AT cannon attack would not have been as steep as a DB attack, it was well capable of attacking at a much steeper angle than most FB. Indeed a shallow dive might not have got much better results than a ground based attack.

37L APCR TK 10 with a +2(CT)/+3(OT) (C7.1 case A +1 plus case B, aerial +1/+2) against the Aerial AF. If you regard the Ju-87 able to point attack from an adjacent hex then an additional +2 for an adjacent hex (1 hex aerial range = 2 hex normal). So you get a modified TK of 12/13 or 14/15 against Aerial AF.

 

[jrv]

BFP put it in as a 37LL, which gives it a TK of 11. According to wikipedia, the gun mounted on the Stuka fired APCR ammunition (https://en.wikipedia.org/wiki/BK_3,7), although I think it had AP rounds too. The muzzle velocity of the gun is higher than for the AT gun (although a range is given for the Stuka gun), so going with the LL may be correct.

JR

 

[Vinnie]

It was the BFP treatment that brought this to mind as I was looking over the Devil's Domain (CH!) rules and my initial thought was that it should be a 37LL (and I persuaded Ian to change it) then I thought that the Germans did not have a 37LL in their armoury. Of course all the L and LL are ASL chrome so it was a case of whcih better modelled the gun's effects.

 

[jrv]

The barrel length system roughly models muzzle velocity (mostly) I imagine, which is why I mentioned it. The 37mm gun on the Stuka was not based on the AT gun but rather on an AA gun. I don't know if they increased the muzzle velocity over the AA gun. If it was firing APCR regularly that would result in much higher muzzle velocity.

JR

 

[Yuri0352]

The gun was an adoption of the 37mm FlaK 18 as the BK 3.7 firing APCR (https://en.wikipedia.org/wiki/BK_3,7). So use the 37L APCR values. Given the ability of the Ju-87 to enter a steep dive you might allow a point attack from an adjacent hex as per E7.403. While an AT cannon attack would not have been as steep as a DB attack, it was well capable of attacking at a much steeper angle than most FB. Indeed a shallow dive might not have got much better results than a ground based attack.

.

Although the 'regular' Stuka was capable of a very steep dive angle, the absence of dive brakes on the 37mm cannon armed variant would seem to indicate that steep dive, point attacks are NA. I'm not an aeronautical engineer, but I would imagine that any 50 degree or greater dive angle in the tank hunting Stuka would be difficult if not impossible to recover from.

 

[Paul M. Weir]

The DB version dived at from 60° to 90°. The idea was to minimise horizontal bomb velocity and thus increase accuracy. I'm envisioning more in the order of 25°-45° for a cannon version and fired at close range. The reason for the close range is simply a much greater need for accuracy, the BK 3.7 only carried 12 rounds per gun. A an angle steeper than normal for a FB also means that more of the thinner roof is visible to the Ju-87.

Maybe 1 (ground) hex might be too much, which is why I only suggested it, maybe starting from 2 or 3 hexes might be better, that will still give a +1 to the modified TK for a total of 13 (CT) or 14 (OT). As the highest Aerial AF is 4, you will do something on a 9 against any tank, a 10 required against a T-34.

Muzzle velocity: Wiki gives 2500 ft/s for the PaK 35/36 and from 2500-2700 ft/s for the FlaK 19/36/37 and practically the same armour penetration. ASL treats both as 37L, which seems right.

 

[jrv]

Muzzle velocity: Wiki gives 2500 ft/s for the PaK 35/36 and from 2500-2700 ft/s for the FlaK 19/36/37 and practically the same armour penetration. ASL treats both as 37L, which seems right.

The muzzle velocity on the Bordkanone 3,7 (BK 3,7) is given as 3,800–2,600 ft/s. I am not sure why it has such a large range, but it is possible the higher value is for APCR.

JR

 

[Paul M. Weir]

The muzzle velocity on the Bordkanone 3,7 (BK 3,7) is given as 3,800–2,600 ft/s. I am not sure why it has such a large range, but it is possible the higher value is for APCR.

JR

The 2600 ft/s would be for AP and HE, 3800 for APCR. Very, very few guns reached near 3k ft/s firing plain AP or HE. Some examples include the 8.8cm PaK 43 L/71 (3300), 7.5cm KwK 42 L/70 (3070) and 17 lbr (2900).

 

[NUTTERNAME]

I believe they removed the air brakes on the tank busters, they really came in at a slow glide and quite low altitude. Worth a look I guess, it seems to show footage of the ground attacks.

The T34 side and rear armor's 'slope' was negated by these attacks. In fact, many T34 were taken out by 20mm attacks on the rear deck, since the 'armor' appears to be actually a vented plate for the blower that produces air flow out the rear.

To use the 37mm Stuka probably took a great deal of skill and experience. Hence the aces that are cited. It seems that it was used in a semiautomatic firing (multiple aimed shots per pass) or even just single shots. Having a water cooled engine would make most ground fire a real danger.

My own take is that they were a very good answer to the Soviet's deep penetration tactics. That is, attack columns that had penetrated the German lines. Less AA to worry about and closer to get back to base.

 

[von Marwitz]

The muzzle velocity of the gun is higher than for the AT gun (although a range is given for the Stuka gun), so going with the LL may be correct.

Regardless of the muzzle velocity, the overall velocity of the round fired would (at least initially) be higher than that of a stationary gun since the Stuka's airspeed would have to be added.

von Marwitz

 

[Paul M. Weir]

Regardless of the muzzle velocity, the overall velocity of the round fired would (at least initially) be higher than that of a stationary gun since the Stuka's airspeed would have to be added.

von Marwitz

In addition, the height of the firer means that gravity adds a bit extra energy, though not as much as the plane's speed.

 

[NUTTERNAME]

The Stuka 3,7cm guns would fire the Tungsten Carbide at something near 1000 m/s. I would wager the Germans, being Germans, would zero the weapons. So they could 'cross' at a typical distance. The air speed would add some velocity, of course, but it is something like 50 M/s. The greatest benefit is the ability to attack the sides and rear and top armor so they act more like vertical armor. Gravity effects are negligible but basically, they might negate the velocity scrub from distance. I would expect any Soviet tank unit to just move as fast as possible and scatter. Even a moving tank could be 'followed' from the rear and the Stuka could stick it regardless. Flight time of the projectiles is very small at these distances. We are probably talking about the firing occurring at 500 meters or less.

 

[witchbottles]

For those with more research time than I , how close was this cannon to the 37mm cannon mounted in the propeller hub of the P-39 Airacobra? That was one powerful shell, but an extremely slow ROF crippled the design vs fast maneuvering targets.

Or perhaps it was a better comparison the Hispano-Suiza 20mm Gun in the Lockheed P-38?
I've not any idea which one is a better comparable design, both served similar purpose.

KRL, Jon H

 

[jrv]

"It fired APCR (Tungsten hard-core) ammunition or high-explosive shells in 37x263B mm caliber at 160 rounds per minute." https://en.wikipedia.org/wiki/BK_3,7

JR

 

[witchbottles]

"It fired APCR (Tungsten hard-core) ammunition or high-explosive shells in 37x263B mm caliber at 160 rounds per minute." https://en.wikipedia.org/wiki/BK_3,7

JR

looks superficially similar to the M4 used in the P39: https://en.wikipedia.org/wiki/M4_cannon

150 rpm ROF with HE, a bit slower with the optional HVAP ammunition

By comparison, the `1946 post-war soviet version had a hi ROF at 400 rpm +/- with AP ammunition.

KRL, Jon H

 

[Paul M. Weir]

Other than calibre, they were fairly dissimilar. Firing HE or plain AP you have the following muzzle velocities:
BK 3.7cm: 2600 ft/s
M3 37mm AT gun M3: 2900 ft/s
M1 37mm AA: 2600 ft/s
M4 aircraft gun: 2000 ft/s
All the above are slightly approximate but quite close
The BK 3.7cm is based upon the German 3.7cm FlaK 18/36/37 which is the 37L AA counter. Both the 3.7cm FlaK and 3.7cm PaK 35/36 (Ger. 37L AT) have fairly comparable AT performance.
The M3 is the US towed 37mm (ASL 37LL) and its tank versions was used in the M3/M5 light and M3 medium tanks.
The M1 is the ASL US 37L AA counter which was superseded by the 40mm Bofors.
The M4 is the aircraft gun as used in the P-39 and P-63.

As you can see, if you check other gun's figures, out most nations' 37mm AT & AA are roughly equivalent at 2500-2600 ft/s and get a 37L. The US M3 has the highest at 2900 ft/s and that is similar to the Panther's and Tiger II's gun and deserves a 37LL. The P-39's M4 armament would only deserve a plain 37.

The M4 was designed as a bomber destroyer. Experiments done on aircraft armament showed that HE did far more damage than piercing rounds. That is why the Germans shifted to lower velocity 30mm in the MK 108 (1770 ft/s) in preference to the higher velocity 20mm MG 151/20 (2300-2400 ft/s) in turn to the 15mm MG 151/15 (2800 ft/s). The disadvantages of the likes of the M4 and MK 108 with lower velocity and high trajectory drop were offset by the far fewer hits required to down a heavy bomber.

Despite previously commonly held assumptions that Soviet P-39 were used in an anti armour role, the Soviets got very little M4 AP rounds, almost entirely HE. So though quite effective against soft ground targets and aircraft, the M4 would have been quite useless against all except the flimsiest of AFV.