Alternative History Armoured Fighting Vehicles Part 3

Oh, VVSS for everything
dquvkvpfcpg41.jpg
Looks pretty cool, not gonna lie.
 
with a transparency of a standard M4A4 place over the pick from Hunnicutt's Sherman on 276, noting size of the VVSS units vs the coil units.
So sot surprising that idea stayed on paper
One again, the size is not what I'm asking about, but the vertical travel that can be achieved by the suspension. Nothing on this picture shows what the travel is.
 
Some reflections on US WW2 tank gun development, might be relevant for AH purposes:

The way the Americans designed the more compact and lighter 76mm M1 from the 3" M7 gun was not purely through better technology, but also a reduction in certain requirements:
1642150841309.png

The 3" case was was designed with a huge safety factor, that is that they didn't fill it with the powder charge as much as they could. The 76 M1 vastly reduced the safety factor, so that it could carry a comparable charge within a smaller case and keep comparable ballistics. This also meant they could reduce the size of the chamber and breech, by 25% in the former's case. The barrel was also thinned out, but I don't know if it was compensated by better steels or if the barrel was just less overbuilt.

The 3" M7 actually had an impressive potential thanks to being so overbuilt. One could remove the distance wad and fill the case with more powder, and the recuperator and buffer were designed to handle 17pdr levels of pressure and recoil.
The Americans actually testing a slightly higher loading (108-115%). In the optimal configuration (where the case was still not filled to the maximum viable), it could increase the velocity of 15lb projectiles to 2800 fps instead of 2600 fps, and actually improve the reliability of case ejection. To the best of my knowledge, the Americans sadly kept the 2600 fps muzzle velocity. 2800 fps would have increased penetration by .5 inches for APC, and .7-.8 inches for HVAP, increasing reliability against a Tiger I from more angles and ranges, Tiger II sides, and a Panther's turret front and mantlet, which were not always easy targets for 2600 fps MV ammo.
This would also have put the 3" M7 just below the British 77mm in terms of penetration, as the latter shot a higher quality 17lb projectile at 2575 fps and penetrated .8 inches more than the normal M7 and 76mm.

However, as I pointed out, the 3" M7 was overbuilt to even handle the 17pdr's power. The Canadians concluded that the US could develop a supercharge to push the muzzle velocity to 3000fps. This could probably still be done with the existing barrel (while retaining good barrel life by British standards at least) and case, with some improvements to other parts here and there. The result would sit between the 77mm and the 17pdr.

The British regularly supercharged their rounds, generally increasing velocity by 200 fps or more for 2pdr, 6pdr, and 25pdr ammunition.
The American obsession with keeping multi-thousand round barrel life in WW2 (as opposed to their postwar guns) led to the M7 in particular being very underpowered for its size and weight.​


However, even a supercharged M7 wouldn't be very efficient by late war, and this where some interesting facts come up.

The 3" was based on the T9 AA gun's barrel which nearly entered production in 1938, but was rejected in favor of the more progressive 90mm gun. The 90mm AA gun would eventually enter service in mid-late 1940, with some modifications in mid-1941. The 3" M7 started development at the same time the 90mm was entering service in AA form, in September 1940 or so.
This means that in theory, the US could simply have developped their new AT and tank gun around the 90mm from the start rather than the rejected 3" barrel from 1938. In practice, the 3" was so overbuilt/inefficient that the 90mm was very similar in bulk and weight, to the point where the US swapped the 3" for a 90mm in the M10 GMC and the M6 Heavy Tank with no issues other than those already present with the 3". Except that in exchange for somewhat heavier and wider ammo, the 90mm offered vastly greater AP and HE capability. The 3" barrel was not mass produced prior to the development of the AT gun, so there wasn't really the advantage of reserve parts being available.

To give some more perspective, the Americans did the exact opposite of what the Soviets did. When the latter introduced the 85mm 52-K AA gun to replace the 76mm 3-K, they cancelled all tank gun projects using the 3-K's ammo and ballistics and launched 85mm gun projects with 52-K ballistics, leading to the D-5T and Zis-S-53 of 1943-44. This was because they wouldn't produce any more parts to sustain a 76mm gun with 3-K ballistics in the future.

The Americans, meanwhile, chose to use a gun that didn't even enter service and had been already displaced, instead of the system that they were making the manufacturing capacity for. They couldn't even synergise with the 90mm industry until designing the 90mm M36 and the M26! All that for an inefficient gun design that was vastly less powerful and future-proof and only offered somewhat greater ammo capacity. At the same time the 3" was in development, the British were developping the 17pdr.

Thus, the choice of the M7 not only prevented an early service entry of a powerful 90mm gun in service (OTL introduction date of the M10 GMC since it could be designed with a 1940-41-designed 90mm from the start), but it led to the idea of developping a more efficient gun with the same ballistics (the 76mm), maintaining the wrong level of firepower in the future. The 90mm T2X could have been developped at the same time the OTL 76 T2X series were, since integrating the 90mm was a matter of upscaling the turret and strengthening the components to the appropriate level. Again, note that the British were developping 17pdr Cruiser tanks since 1941.

The US was a country with such a huge and safe industrial capacity that it could pretty much achieve what the British always wanted, except faster, but it was also the only country that actively denied itself such an increase in firepower.



 
case length and base diameter and chamber pressure
M1 76mm 76x539R 90mm dia, 43,000
M5 3” 76x583R 108mm dia 38,000
17 pdr 76x583R 135mm 47,000
M3 90mm 90x600R 130mm dia 38,000

38,000 was the same pressure as the M3 75mm
 
The US was a country with such a huge and safe industrial capacity that it could pretty much achieve what the British always wanted, except faster, but it was also the only country that actively denied itself such an increase in firepower.
The amusing paradoxes created by a nation with such industrial capacity but a government categorically allergic to spending money on the military until a war actually breaks out (oh how times have changed!).
Even then I think the issue is very much along the lines of why Britain was still using the SMLE and the .303 in 1945 despite a viable and proven superior replacement developed prior to the last war: the perceived costs of replacing established reserve stocks of arms and ammunition were deemed prohibitive, so they didn't bother. Yes, the US could have developed and fielded a 90mm tank gun from 1940 onwards, but that would mean spending money (gasp, horror) and getting rid of the 3" ammunition they already had (swoon, faint).
 

Driftless

Donor
Wasn't/isn't there a business economics mentality at work in many of those situations? Keep costs to an absolute minimum, spending juuuuuuuusssst enough to accomplish the end goal, while maximizing profits. All jokes aside, military success doesn't usually work on that line.
 
The amusing paradoxes created by a nation with such industrial capacity but a government categorically allergic to spending money on the military until a war actually breaks out (oh how times have changed!).
Even then I think the issue is very much along the lines of why Britain was still using the SMLE and the .303 in 1945 despite a viable and proven superior replacement developed prior to the last war: the perceived costs of replacing established reserve stocks of arms and ammunition were deemed prohibitive, so they didn't bother. Yes, the US could have developed and fielded a 90mm tank gun from 1940 onwards, but that would mean spending money (gasp, horror) and getting rid of the 3" ammunition they already had (swoon, faint).
I'm not even sure the tank and anti-tank 3" used any ammunition or component of the old AA guns though. Hearings from 1940 only refer to AA and special HE ammo, and I'm not sure they shared the exact same case. The barrel itself is new, and the rest of the components came from the HM2 howitzer or were new.

It's not even just prewar, that conservatism was prevalent at least in Army Ordnance through the whole war. Though things were kinda whack between 1936-40 too.
 
Something I think would be interesting would be seeing the sort of tanks that would be made with an early 1900s (like, 1903) level of technical sophistication, but knowing everything that is known now about doctrine and design.

Perhaps a riveted design might be used, simply because welds of superior quality are too difficult to make in numbers. Thoughts?
 
Something I think would be interesting would be seeing the sort of tanks that would be made with an early 1900s (like, 1903) level of technical sophistication, but knowing everything that is known now about doctrine and design.

Perhaps a riveted design might be used, simply because welds of superior quality are too difficult to make in numbers. Thoughts?
With realy early 20th century tech you will quickly run into serious problems with regards to engines and transmissions for one. Their power, weight and reliability is much worse than even during WW1 and I dont think even advanced design knowledge could compensate for these shortcommings
 
I'm not even sure the tank and anti-tank 3" used any ammunition or component of the old AA guns though. Hearings from 1940 only refer to AA and special HE ammo, and I'm not sure they shared the exact same case. The barrel itself is new, and the rest of the components came from the HM2 howitzer or were new.

It's not even just prewar, that conservatism was prevalent at least in Army Ordnance through the whole war. Though things were kinda whack between 1936-40 too.
Fair point, but I stand by institutional reticence to adopt an entirely new class of ammunition, even if the conservative alternative is only 'the same' as existing stocks if you squint at the accounting ledger in poor lighting.
Something I think would be interesting would be seeing the sort of tanks that would be made with an early 1900s (like, 1903) level of technical sophistication, but knowing everything that is known now about doctrine and design.

Perhaps a riveted design might be used, simply because welds of superior quality are too difficult to make in numbers. Thoughts?
@Leander has it: the limiting factor is the engine. You really need those ten years of additional development before IC engines have the grunt to make a fully armoured vehicle viable, and despite its proven power there are all kinds of issues with using steam which is why that wasn't used OTL either.
 

Driftless

Donor
@Leander has it: the limiting factor is the engine. You really need those ten years of additional development before IC engines have the grunt to make a fully armoured vehicle viable, and despite its proven power there are all kinds of issues with using steam which is why that wasn't used OTL either.
A kerosene or fuel oil powered steamer, a little less likely to whoooof on being hit? Probably more so in the prime mover or even SPG role?
 
A kerosene or fuel oil powered steamer, a little less likely to whoooof on being hit? Probably more so in the prime mover or even SPG role?
The problem is the pressurized steam, not the fuel. There's a good reason why in rail locomotives the cab is usually as far away from the pressurized bits as reasonable.
Steam tractors for hauling artillery were regularly used so no issue there, but you never want to have one somewhere it might get shot, the resulting steam explosion might do more harm than the shell that opened it up might have.
 
Fair point, but I stand by institutional reticence to adopt an entirely new class of ammunition, even if the conservative alternative is only 'the same' as existing stocks if you squint at the accounting ledger in poor lighting.
I'm not sure about the complete veracity of it, but it seems that the 3" initially wasn't accepted by any of the US branches, mainly due to weight and bulk reasons.
Considering how the US proposed 3000 fps 3" guns in 1942 and 1944 and the 76 M1 was developped to keep the same ballistics and projectiles as the 3", it seems to me that the reason they went with the 3" then is because they always wanted that caliber from the start (probably to have more ammo capacity, they were obsessed with that), initially didn't think they needed more than 2600 fps and would rather get a more compact and lighter gun to keep TDs and tanks as light as possible.

With that narrative, the 90mm caliber was less convenient and the gun couldn't be any lighter than the 3" M7, so it would never meet requirements for a much lighter and smaller weapon. At least until they started looking at it in April 42.

That doesn't change my point that they underestimated future firepower needs obviously and that a British or Soviet in that position would do differently, but that might explain their line of reasonning then.
 

Garrison

Donor
Well the idea was certainly around at the time, HG Wells wrote about land ironclads involved in future battles in a short story published in 1903. So I suppose if the idea grabbed the imagination of someone influential it might not be impossible for that to lead to a functional design that was less grandiose than Well's description.
 
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