Casemate M4 Sherman tank destroyer

The TD casemate M4 shall hereafter be referenced as the “Shermgeschutz”.

The M4 chassis was used for open-topped SPA, and for open-topped turreted tank destroyers. What if US doctrine instead or additionally used fully enclosed, casemate Sherman-based tank destroyer?

Perhaps late-war, it could be equipped with a different transmission allowing for in-place traversal and a lower profile? Might an M4A3 based version survive into the Korean War?

Would it be able to carry a 90mm gun? Or would it need to be a 76mm gun? Would the US put an MG turret on it? Would it be possible to make the frontal armor
 
Would it be able to carry a 90mm gun? Or would it need to be a 76mm gun? Would the US put an MG turret on it?
Yes easily, no, definitely early on in the war!

I would suggest that an M3 early on without the small turret might be a good start for the idea, maybe fit an old navy 3"?
 
Yes easily, no, definitely early on in the war!

I would suggest that an M3 early on without the small turret might be a good start for the idea, maybe fit an old navy 3"?

How much better than the 75mm would the navy 3” be?

What about the M1918 AA gun, like on the M10?
 
Could you remove turret of the M3 & places 17 pounder in the sponson?

Canadian trialled a 3.7in AA gun on it.

Dsc02780_-_ram_gun.jpg
 
Could you remove turret of the M3 & places 17 pounder in the sponson?

I feel like it would be too big. Also, it was used 1943 onwards, which means more fireflies is a better choice, or at least mounting it in a more modern hull.
 
How much better than the 75mm would the navy 3” be?
75mm L/31 (M2) 563 m/s (1,850 ft/s) with shell 6.32 kg (13.9 lb) M72 AP-T
v
3-inch M1918 2,400 ft/s (730 m/s) with a 15 lb (6.8 kg) shell
v
3″/50 2,700 feet/s (820 m/s) with a 13.1 lbs. (5.9 kg) shell edited

So much more powerful at the cost of extra weight.

If you cant ask the navy why not the army 3-inch gun M1903 from the Army Coast Artillery Corps.
2,800 ft/s (850 m/s) with 15 lb (6.8 kg) shell
 
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With 90mm gun and serious frontal armor, it would be a welcomed addition to the US arsenal, helping in the roles filled by the Jumbo and the 105 assault gun variant as well as the TD role! But, the doctrine associated with the TD role would need some re-examination and re-imagining. The US would need to arrive at the "move aggressively, fight defensively" posture all the other operators of casemated weapon systems reasonably adopted.
 
I feel like it would be too big. Also, it was used 1943 onwards, which means more fireflies is a better choice, or at least mounting it in a more modern hull.

Fireflys weren’t ordered until February ‘44 whereas the 17 pounder was available November ‘42 as trialed on the AC4.
Though you may indeed the amount of recoil May make it too big, but definitely would’ve been worth a try.
 
Could you remove turret of the M3 & places 17 pounder in the sponson?

Almost there

The M9, M3 Medium with a 3" gun. 1000 ordered, but cancelled on supply issues with the 3" gun
636px-3-inch_Gun_Motor_Carriage_M9.png

Build the Chassis, make available for LL then send them to Canada to get 17 pdrs. The weight of the gun was very similar
 
The TD casemate M4 shall hereafter be referenced as the “Shermgeschutz”.

The M4 chassis was used for open-topped SPA, and for open-topped turreted tank destroyers. What if US doctrine instead or additionally used fully enclosed, casemate Sherman-based tank destroyer?

Perhaps late-war, it could be equipped with a different transmission allowing for in-place traversal and a lower profile? Might an M4A3 based version survive into the Korean War?

Would it be able to carry a 90mm gun? Or would it need to be a 76mm gun? Would the US put an MG turret on it? Would it be possible to make the frontal armor
Claymore built a model of a Shermgeschutz, you can see pics of it here https://www.alternatehistory.com/forum/threads/completed-ah-afv-models.271038/
 
Fireflys weren’t ordered until February ‘44 whereas the 17 pounder was available November ‘42 as trialed on the AC4.
Though you may indeed the amount of recoil May make it too big, but definitely would’ve been worth a try.
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17-pounder gun needed a major re-design to cram it into a stock Sherman turret. Even with all the re-design, the Firefly turret was cramped and awkward.
An M3 Firefly could be introduced as much as two years ago earlier because it did not require modifying the gun. Since an M3 Firefly might retain the 37 mm turret, that could still fire HE at infantry-designated targets.
Let the Canucks have a try!
 
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17-pounder gun needed a major re-design to cram it into a stock Sherman turret. Even with all the re-design, the Firefly turret was cramped and awkward.
An M3 Firefly could be introduced as much as two years ago earlier because it did not require modifying the gun. Since an M3 Firefly might retain the 37 mm turret, that could still fire HE at infantry-designated targets.
Let the Canucks have a try!

There was no spare room in an M3. The Cheiftain did a 3 part video on the Grant and the gunners and loaders position for the 75mm was incredibly cramped because of the turret basket for the 37mm.

 
With how tall the Sherman was, how low could a casemate actually be?

With the turret removed the casemated Sherman wouldn't be beat tall. Place the gun where the assistant driver was. In one of the Chieftan's talks about US armour in WWII he brings up pictures of three tanks and the gunners sight. Of the three. The Sherman was the only one with a top mounted sight. The rest of the talks are very illuminating. Was the Sherman perfect, of course not. Was it reliable, sure was. Was it a complete death trap? Given my uncle bailed out of three of them and survived each time I'd say no. The Sherman of 1945 is in no way the Sherman of 1942.
 
I'd really like to see a Navy 5"/25 mounted on a Sherman hull. 54lb shell at 2100fps.

The hull can handle the weight (for example, the Jumbo's turret weighed over 20,000lbs), but it might be too large (11ft 10")
 
With the turret removed the casemated Sherman wouldn't be beat tall. Place the gun where the assistant driver was. In one of the Chieftan's talks about US armour in WWII he brings up pictures of three tanks and the gunners sight. Of the three. The Sherman was the only one with a top mounted sight. The rest of the talks are very illuminating. Was the Sherman perfect, of course not. Was it reliable, sure was. Was it a complete death trap? Given my uncle bailed out of three of them and survived each time I'd say no. The Sherman of 1945 is in no way the Sherman of 1942.

So just rejiggering the internal arrangement after removing the turret would make enough room? Or would it need a superstructure like in claymores model? Would the non superstructure version be able to fit a 90mm (Perhaps a new short n’ fat case version could be developed) or would it be limited to a 76.2mm?

Also, what sort of armour would the US give it? Maybe they could be built off of Jumbo hulls with the turret removed, making a combined TD/Assault gun?

Also, what sort of mantlet makes sense?
 
Delete the darned turret, and there is plenty of room in the hull for a rear end of a bigger cannon. Go to the field and kill German tanks and whatnot.
 
I'd really like to see a Navy 5"/25 mounted on a Sherman hull. 54lb shell at 2100fps.

The hull can handle the weight (for example, the Jumbo's turret weighed over 20,000lbs), but it might be too large (11ft 10")

I think the 5”/38 might actually be better and easier to fit, since it used semi-fixed ammo instead of fixed.
 
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