Help with armored AA and AAA vehicle designs.

Hello all, I just re-read some accounts of how the Japanese managed to beat up the US airfields in the PI, Midway, and Dutch Harbor, and I have to admit I was shocked to learn just how pathetic the US anti-air defenses performed, while at the same time just how effectively the Japanese zeros reduced what the bombers missed.

Specifically, what kind of armor would be immune to a Zero’s 20mm cannon? I am throwing this out there: Think ‘TANK’, and then go with an outer armored plate, meant to deform/slow the cannon shell, then a layer of ‘end on’ sandbags in racks built onto the hull, and then the armored hull itself. The outer armored plates would be the hinged ‘doors’ giving access to the sandbagged racks mounted on the sides of the hull, while the top of the hull would have at least a double stacked layer of sandbags between the outer armored plate and the hull itself. So, would it be possible to make such a vehicle immune to the early war A6M’s 20mm cannons, and if so how thick would the armored plates and armored hulls need to be to achieve this with a bit of over-engineered safety factor tossed in?
I just assume that you cannot hope to build a bomb proof vehicle (or bunker, for that matter), and so want to posit a well armored, highly mobile force of AA and AAA forces, that can be moved in the middle of an attack, between attacks, and easily dispersed or concealed as the need arises, unlike the OTL fixed emplacements.


I would like to hear folks ideas for mobile anti-aircraft, armored vehicles, configured either as:
Mark I, an anti-strafing defense, against low level fighter attacks.
Mark II, an anti-CAS defense, against low level (or dive) bomber attacks.
Mark III, an anti-bomber defense, against high level bomber attacks.

As for armaments, what would the three types likely need to be armed with, for optimal results?
My own thoughts have not really considered the Mark II and Mark III variants, but for the anti-fighter ones, would 8 .50 cal M2’s seem about right? What I am looking for here is not the minimum firepower needed, but something more like the maximum we could fit on. I would want any Japanese fighter pilot to have a VERY bad day should he have the misfortune to find himself on the receiving end of even a short burst from one of these bad boys. At first I was thinking that you could possibly (hopefully) just switch out the turrets between the types, but I’m not so sure now that the differing armaments would allow for that. Anyway, for the Mark III, say you wanted an AAA weapon to engage bombers at 20,000 + feet, what would you need in late 1930’s early 1940’s to get this done, and yet be able to be mounted upon a tank chassis for mobility/survivability? I’m thinking the equivalent of a SPG here, but an AAA weapon rather than conventional artillery, that would need to be able to be fired and loaded in a near vertical, and have only slight elevation adjustments, yet being able to track (rotate) a bomber formation. For the Mark II, I’m thinking that you would need/want a lighter cannon, with fast traverse and full elevation capabilities, and possibly some M2 .50 cal as well?

Later on I’ll post the questions I have of doctrine, training, and support forces.
 
SPAAG make little sense in the Pacific. Given the vulnerability of Japanese Aircraft, the use of large numbers of HMG for close defence, along with well sited 40mm AA guns would be the ideal solution against straffing.

Instead of deploying a 20t AFV, it would be better to give crews of 40mm guns a few shovels and axes, so they could work on improving their positions.

Bofors1.jpg
 
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If you really insist on SPAAG, this was the OTL answer to your exact requirement, the Canadian AA Grizzly Skink (Canadian Sherman).

grizzly-skink-aa-01.png
 
Specifically, what kind of armor would be immune to a Zero’s 20mm cannon?

The far more powerful 20mm Flak 30 AP round did 14mm at 500 Meters.

The Type 99 with AP did around 9mm

The thinnest armor is on the M4 top engine deck, at 18mm

The Stuart is 13mm
 
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