Sir John Valentine Carden survives.

True, assuming you have the capacity. OTOH, the resources you spare on those guns could maybe make a significant difference elsewhere.


Who said anything about tanks? I was just talking about guns.
Considering OTL Britain adopted the OQF 75 over the 75 m3 it is safe to say that resource spent to make modified 6lbers were more preferable than modifying the turrets of every tank they wanted to arm with a 75mm gun.
 
I really don't get all the love given to what is essentially a 40 year old French Field Gun.

The fact that it gives the Valiant I the capacity to fire a decent HE shell and still be more than capable of dealing with the Panzer III/IV. As was said in the story earlier, Carden's team said that fitting the 3-inch Vickers in would reduce space in the turret to a 2 man crew. 2-man turrets are bad, very very bad, and I have a feeling the battle of france will highlight that. Being able to fire that shell is a useful stopgap whilst the Valiant II, or whatever its renamed to be is designed, tested and built. In the meantime, the UK can use the 6lb gun as well as having the option to fire a 75mm shell from a bored out version of the gun on the same mounting that won't screw up the internal space and make it a cramped mess with an overworked tank commander.

I recognise that the 6lb or rebored 75 is basically an intermediary gun, and honestly, going straight to the vickers 75 hv is probably going to be a bit too much of a wank which this TL seems to be trying to avoid just doing a tit job of the UK's performance in WW2. The 6lb will be replaced by 43/44 by the bigger HV gun whatever type of weapon it is, but until then the 6lb will carry the burden for British forces. And even if they fiddle with the shell to make it a better HE round, a 75 is still a bigger bang.

Also the 6lb/rebore option allows for a smaller Cruiser like the Cromwell, if something like it appears TTL to be fitted with the same gun, again without messing up the internals. Hell you could produce the Valiant Mk 3 in a 1 - 3 ratio, 1 x 75 firer and 3 x 6lb armed tanks so that squadrons will have a 'CS' tank with them. Or even design the breech so that you can swap it out in the field and replace one barrel with the other for flexibility.

The UK still has its doctrine of CS tanks, but that'll fade as the need for a good HE round is recognised and the 75 shell fired by the Sherman/Grant is a good HE round and if the Valiant Mk 3 or whatever version of it that gets fitted with the 6lb gun can also get fitted with a re-bored 6lb to fire the US 75mm shell, then this gives the UK a very good hole puncher and adequate HE lobber and another tank with a good hole puncher and, very good HE lobber, without having to majorly alter the tank as its already got the growth there for the rebored gun.

This will suit UK armoured forces fine and do very well against anything barring Tiger and Panther in frontal battles, and will give the UK time to develop a tank that can carry the bigger and more powerful Vickers weapon and NOT have it be a bodge job, but designed with thought and care to give the UK and WAllies a tank that is more than capable of engaging the bigger German tanks when they make an introduction, especially as ammunition improves.
 
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I think people are assuming that the 3incher will be fitted to the valiant and are making rather meh assumptions to be honest. I would think it would best fit for the valiant successor tank instead and be out like in 1943 maybe and be the main tank for d-day invasion ?

And if the author wants he can make battle of france alot more costly to the germans if he wants to cause honestly the otl battle of france was more or less ASB like rather than a normal campaign . People seem to forget that the BEF and the best of frances armies barely fought at all and the panzers attacked 2nd or 3rd rate armies mainly .
 
1) They weren't shy about a lot of things relating to tanks, which is why so many are rightly regarded as poor.
2) You're supposing (without any real evidence) that it's possible.
3) The American 75 will fit in the Vickers I turret with limited modification, and retain decent ergonomics. The Vickers 75 will take rather more work, and the ergonomics will likely be pretty crummy. In addition, the British are likely to not be in such a "we need this NOW" mindset, because the Valiant is actually a good tank.
4) You're assuming an all-or-nothing adoption, but you remove a lot of those issues by just arranging mixed squadrons.
5) True. OTOH, they'll come in with the American troops, so there's going to be exposure regardless.

Also, you're forgetting that the USA has far more resources to hand, while the Vickers team is struggling just with their pre-war orders.

1) Most of the reason the UK tanks were considered poor was the situation they found themselves in during the war. The whole loosing all you're heavy equipment and having to start from scratch coupled with invasion scare made Britain make choices it wouldn't have done had it had time on it's hands. Then you have kludges like the firefly, an inelegant solution that dealt with the problem of Panther and Tiger now with a compromised solution rather than not dealing with them now whilst waiting for the perfect solution.

2) It is possible. How it is done depend's but it will be possible to get the new gun into the Valiant. If that's as a 2 man turret, a firefly like ergonomic nightmare, a major modification to the tank or some other solution it will fit. The question becomes what will be acceptable versus what is possible in the time and with the resources allowed.

3) Work on getting the Vickers design into a tank/the Valiant will have started long before the UK has encountered the US 75. That process could already have produced a follow on tank that is accepted and production is starting to be set up to produce it when the British encounter the US 75. It may be that the UK might reach the point of deciding the 75 is better than the 6pdr as the Valiant's follow on is just starting to roll of the production lines. If that's the case or close enough then your expecting Britain to stop work on it's new tank in order to develop a slightly better gun for it's old ones. In addition the one thing Britain was good at during the war was preparing for the next tank. That's why the firefly and Challenger were built prior to D-day and how the British had over 100 17pdr's built and able to be sent to North Africa when Tiger 1 shows up. In getting something ready soon to counter a likely threat Britain accepted the less than ideal.

4) I'm assuming a timeline that has the UK moving away from the 6pdr and tanks that can only carry it at a similar time the 75 becomes accepted. in that scenario the resources are better spent on replacement tanks rather than designing a new gun and ammo stowage for the outgoing tanks.

5)Possibly, one thing we haven't discussed is the possibility of the US adopting the Vickers design. OTL the US wasn't against adopting British gun's (at least early war), they did with the 6pdr. Yes the didn't adopt the 17pdr but that's less because of the gun and more because of it's mounting. TTL the Vickers design is likely ready and being produced before the Sherman is in production. If asked it is possible the US will put the Vickers design in the Sherman, it would fit and is a better dual purpose design. If america adopts the Vickers then the US 75 may only see limited action. It does't become a major part of the war and nobody see's its potential.
 
The fact that it gives the Valiant I the capacity to fire a decent HE shell and still be more than capable of dealing with the Panzer III/IV. As was said in the story earlier, Carden's team said that fitting the 3-inch Vickers in would reduce space in the turret to a 2 man crew. 2-man turrets are bad, very very bad, and I have a feeling the battle of france will highlight that. Being able to fire that shell is a useful stopgap whilst the Valiant II, or whatever its renamed to be is designed, tested and built. In the meantime, the UK can use the 6lb gun as well as having the option to fire a 75mm shell from a bored out version of the gun on the same mounting that won't screw up the internal space and make it a cramped mess with an overworked tank commander.

I recognise that the 6lb or rebored 75 is basically an intermediary gun, and honestly, going straight to the vickers 75 hv is probably going to be a bit too much of a wank which this TL seems to be trying to avoid just doing a tit job of the UK's performance in WW2. The 6lb will be replaced by 43/44 by the bigger HV gun whatever type of weapon it is, but until then the 6lb will carry the burden for British forces. And even if they fiddle with the shell to make it a better HE round, a 75 is still a bigger bang.

Also the 6lb/rebore option allows for a smaller Cruiser like the Cromwell, if something like it appears TTL to be fitted with the same gun, again without messing up the internals. Hell you could produce the Valiant Mk 3 in a 1 - 3 ratio, 1 x 75 firer and 3 x 6lb armed tanks so that squadrons will have a 'CS' tank with them. Or even design the breech so that you can swap it out in the field and replace one barrel with the other for flexibility.

The UK still has its doctrine of CS tanks, but that'll fade as the need for a good HE round is recognised and the 75 shell fired by the Sherman/Grant is a good HE round and if the Valiant Mk 3 or whatever version of it that gets fitted with the 6lb gun can also get fitted with a re-bored 6lb to fire the US 75mm shell, then this gives the UK a very good hole puncher and adequate HE lobber and another tank with a good hole puncher and, very good HE lobber, without having to majorly alter the tank as its already got the growth there for the rebored gun.

This will suit UK armoured forces fine and do very well against anything barring Tiger and Panther in frontal battles, and will give the UK time to develop a tank that can carry the bigger and more powerful Vickers weapon and NOT have it be a bodge job, but designed with thought and care to give the UK and WAllies a tank that is more than capable of engaging the bigger German tanks when they make an introduction, especially as ammunition improves.

The thing is the timeline for Britain adopting the US 75mm makes no sense. TTL it is mid 1939 and Vickers are already looking at the design of the 77mm HV (well something likely very similar) so it could well be coming off production lines in late 40 or early 41. That's before the Sherman has entered production and TTL the M3 medium is likely to be avoided by the British for a number of reasons. I also suspect that Carden will be starting the design process for a the replacement for the Valiant some time in the not too distant future. It will be consistent with what we have seen from him so far. That could get you the replacement Valiant rolling off the production lines armed with the 77mm HV sometime in late 42 or early 43. OTL the UK didn't get the US 75 into active service until early 42, TTL that may be delayed because Britain is in a less dire tank situation.
It could well be that by the time the US 75mm has proved itself to the British they are already in the process of moving past it. At that point why would you stop moving past the 6pdr/75mm to change the gun on the 6pdr armed tanks when you can instead focus those resources on the new tank and gun? It makes no sense.
Basically
mid-39 77mmHV development starts.
Late 39 Valiant successor development starts
mid40- 77mm HV ready to start production
Late40/early 41 77mm HV starts to come off the production lines.
Late 41/early 42 New Tank design is ready.
Early 42 is when the UK OTL got the US 75mm into combat, likely butterflied in this timeline.
mid to late 42 UK gets first look at 75mm in combat.
Late 42/early 43 New tank with big gun starts coming off production lines

The UK wont immediately fall into line with what this forum wants and declare the US 75 THE tank gun and drop everything to produce it. It will take time, say 6-9 months and another 3-9 months to get a gun capable of using that shell into combat. that takes you well past the point of it being a useful stopgap and into the territory of it being a drain on resources.

That's to say nothing of the possibility of the US adopting the Vickers 77mm HV.
 
Why do you keep insinuating that I think the US 75 is tHe BeStEsT gUn EvAr. Its not so stop trying to be coy about it with the snide comments. We don't know what effect the War will have, we don't know what the fall of France will cost the UK's armoured forces or if there will be a panic which slams the brakes on any development for stuff needed NOW.
I'm a bloody Brit so I don't think that the Sherman is the be all and end all either so none of that crap either.

But, what I think is that the 6lber will be with British forces for longer than you're predicting, mainly because the pressures of war will mean that any switch over to producing the Valiant replacement will take longer and it'll be more towards 43/44 by the time its ready without it being rushed. Yes they're looking at it now, but they've not got the hull that can carry it yet. Until they do, you've got to use the 6lb gun. And even if you fiddled with its HE shell to make it more effective its still a 57mm shell. The rebored 6lb fiting the 75mm is a superior HE and infantry supporting weapon, we know this from WW2, sure its not as good an AT weapon, but its still adequate until the Tiger and Panther come along whilst the 6lb will do better against those tanks with better ammo.
 
Just some more thoughts on possible logical gun choices for JVC. At this time the standard tank gun is the QF 2lb. The development of what became the QF 6lb did not even start till 1938 and if Sir John is appraised of this work he will know that the gun will not be in series production till probably late 1940. Is he going to wait till then? If he is not then what are the alternatives. In 1938 the Vickers 75mm AA and the 3" AA are both available but are way to much gun of a tank at that time INVHO. Why do you need such a huge leap in calibre even if you want a better HE shell. The logical choice is a gun with AT capability at least equal to the 2lb gun and firing a much more effective HE shell. The logical choice is the 6lb QF Hotchkiss Naval Gun. Vickers Armstrong had built these for the RN and AFAIK were still offering an updated version at this time.
So for Sir John to select this gun for his up-gunned tank is logical, so is his intention to work on fitting the new more powerful QF 6lb antitank gun when it arrives. Later with war experience we could see the same progression as in OTL to the bored out 6lb gun remembering that it uses the same 57 x 441 rimmed case simply necked out to fit the available 75mm shell. I can still see this being done for fitting to tanks that cannot be fitted with the next generation 75mm HV gun which ITTL Sir John Carden will have Vickers working on from much earlier on. also early adoption of the 6lb (Hotchkiss/Vickers)armed tank could well be on the scale of the CS tanks of OTL with similar reasoning. As both the 2lbHV and the 6lbMB are found inadequate against PZIV's then the 6lb HV will come in quickly.
 
1) Most of the reason the UK tanks were considered poor was the situation they found themselves in during the war. The whole loosing all you're heavy equipment and having to start from scratch coupled with invasion scare made Britain make choices it wouldn't have done had it had time on it's hands. Then you have kludges like the firefly, an inelegant solution that dealt with the problem of Panther and Tiger now with a compromised solution rather than not dealing with them now whilst waiting for the perfect solution.
And ITTL they're likely to be much less pressed for equipment, and the equipment on offer is better.

2) It is possible. How it is done depend's but it will be possible to get the new gun into the Valiant. If that's as a 2 man turret, a firefly like ergonomic nightmare, a major modification to the tank or some other solution it will fit. The question becomes what will be acceptable versus what is possible in the time and with the resources allowed.
The war office might, but the war office hasn't put out a specification for anything even close to that yet, and Carden seems more inclined to consider actual combat effectiveness of the crew.

3) Work on getting the Vickers design into a tank/the Valiant will have started long before the UK has encountered the US 75. That process could already have produced a follow on tank that is accepted and production is starting to be set up to produce it when the British encounter the US 75. It may be that the UK might reach the point of deciding the 75 is better than the 6pdr as the Valiant's follow on is just starting to roll of the production lines. If that's the case or close enough then your expecting Britain to stop work on it's new tank in order to develop a slightly better gun for it's old ones. In addition the one thing Britain was good at during the war was preparing for the next tank. That's why the firefly and Challenger were built prior to D-day and how the British had over 100 17pdr's built and able to be sent to North Africa when Tiger 1 shows up. In getting something ready soon to counter a likely threat Britain accepted the less than ideal.
One thing the British never prepared for was enemy AT guns.

4) I'm assuming a timeline that has the UK moving away from the 6pdr and tanks that can only carry it at a similar time the 75 becomes accepted. in that scenario the resources are better spent on replacement tanks rather than designing a new gun and ammo stowage for the outgoing tanks.
'Moving away from' a vehicle takes time. And even when the vehicle is out of production, replacement parts will be coming down the line until all the vehicles in service have been replaced. I wouldn't be especially surprised to still bee the Valiant I in use by whatever is this timeline's equivalent of D-Day.

5)Possibly, one thing we haven't discussed is the possibility of the US adopting the Vickers design. OTL the US wasn't against adopting British gun's (at least early war), they did with the 6pdr. Yes the didn't adopt the 17pdr but that's less because of the gun and more because of it's mounting. TTL the Vickers design is likely ready and being produced before the Sherman is in production. If asked it is possible the US will put the Vickers design in the Sherman, it would fit and is a better dual purpose design. If america adopts the Vickers then the US 75 may only see limited action. It does't become a major part of the war and nobody see's its potential.
The Americans refused point-blank to accept the 76mm in the modified M4 turret, and it wasn't until someone had the bright idea of mounting the T23 turret that they finally accepted it, and even then, they had sufficient concerns that the initial idea of shifting all production to 76mm was reduced to one in three tanks being 76mm. That last one was probably a good idea, as the Germans produced a total of fewer than 8,000 heavy tanks (Panther, Tiger I, Tiger II), most of which ended up on the Eastern Front. And those are really the only targets against which a high velocity gun like the 76mm or 17 pounder excelled, against everything else, the Panzer IV, etc. The 75mm M3 worked perfectly adequately, and had the advantage that the HE shell could actually deal with the real danger to vehicles on the advance, Anti-tank guns.

The thing is the timeline for Britain adopting the US 75mm makes no sense. TTL it is mid 1939 and Vickers are already looking at the design of the 77mm HV (well something likely very similar) so it could well be coming off production lines in late 40 or early 41. That's before the Sherman has entered production and TTL the M3 medium is likely to be avoided by the British for a number of reasons. I also suspect that Carden will be starting the design process for a the replacement for the Valiant some time in the not too distant future. It will be consistent with what we have seen from him so far. That could get you the replacement Valiant rolling off the production lines armed with the 77mm HV sometime in late 42 or early 43. OTL the UK didn't get the US 75 into active service until early 42, TTL that may be delayed because Britain is in a less dire tank situation.
It could well be that by the time the US 75mm has proved itself to the British they are already in the process of moving past it. At that point why would you stop moving past the 6pdr/75mm to change the gun on the 6pdr armed tanks when you can instead focus those resources on the new tank and gun? It makes no sense.
Basically
mid-39 77mmHV development starts.
Late 39 Valiant successor development starts
mid40- 77mm HV ready to start production
Late40/early 41 77mm HV starts to come off the production lines.
Late 41/early 42 New Tank design is ready.
Early 42 is when the UK OTL got the US 75mm into combat, likely butterflied in this timeline.
mid to late 42 UK gets first look at 75mm in combat.
Late 42/early 43 New tank with big gun starts coming off production lines

The UK wont immediately fall into line with what this forum wants and declare the US 75 THE tank gun and drop everything to produce it. It will take time, say 6-9 months and another 3-9 months to get a gun capable of using that shell into combat. that takes you well past the point of it being a useful stopgap and into the territory of it being a drain on resources.

That's to say nothing of the possibility of the US adopting the Vickers 77mm HV.
You're making a big hoo-rah about this experimental Vickers design, yet you have no idea if it can even be fitted into the Valiant I (it probably can't, not without making unacceptable compromises). That being the case, the 75mm is a perfectly acceptable weapon, given that most of the targets these things are going to be facing are not tanks, and thus don't need the punch of even the 6-pounder to kill.
 
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The Americans refused point-blank to accept the 76mm in the modified M4 turret, and it wasn't until someone had the bright idea of mounting the T23 turret that they finally accepted it, and even then, they had sufficient concerns that the initial idea of shifting all production to 76mm was reduced to one in three tanks being 76mm. That last one was probably a good idea, as the Germans produced a total of fewer than 8,000 heavy tanks (Panther, Tiger I, Tiger II), most of which ended up on the Eastern Front. And those are really the only targets against which a high velocity gun like the 76mm or 17 pounder excelled, against everything else, the Panzer IV, etc. The 75mm M3 worked perfectly adequately, and had the advantage that the HE shell could actually deal with the real danger to vehicles on the advance, Anti-tank guns.


You're making a big hoo-rah about this experimental Vickers design, yet you have no idea if it can even be fitted into the Valiant I (it probably can't, not without making unacceptable compromises). That being the case, the 75mm is a perfectly acceptable weapon, given that most of the targets these things are going to be facing are not tanks, and thus don't need the punch of even the 6-pounder to kill.
I am also less enthusiastic about the Vickers gun. It's worth noting that the engineering team merely evaluated the possibility of using this weapon, there hasn't been any specific order to start development, and given that integration of the 6pdr will have to be done first, and that Vickers is working on many other things it's not a given that the resources will be allocated to the Vickers 3" yet. Add in the development of a new tank which may feature many serious improvements that lengthen the time to put it into production, and it's more likely that the gun and tank enters service in mid to late 1942 like the long 75 Pz IV, or the Sherman 76 if the US had accepted its limitations.

As for the latter, it can be argued that the Americans wasted much of the benefit of getting a long 76 by taking so long to approve an adequate turret and mounting for it. As far as I know, even after the Quick Fix turret was rejected nothing was done to develop an adequate turret for the Sherman specifically, it just benefitted from the T23 turret, and there is a rather serious gap I think between the rejection of the Quick Fix (which was still better than the postwar NATO 76 Shermans with the small turrets) and the development of the T23 turret.
As for why I said it was wasted, it's because while the gun itself was fully developped in terms of raw power (cartridge size, barrel length, operating pressure) by 1942, none of the vehicles or turrets that were supposed to accept it entered production before late 1943, but no effort was made to increase the gun's power in the meantime. The result is that the reasonnable concept of a lightweight and more compact 3" M7 that would be easier to use (and thus should be able to be used quickly) became obsolescent in the face of German tank uparmouring by the time it was deployed. They had to restart all over again to fully counter German armor with the 90mm gun, and even that was difficult because gun production stopped before the need for the 90 as an antitank gun was notified, no US vehicle was purposely designed for it (bar the Jackson. T25 and T26 don't count because they mostly kept a hull design intended for a 76mm gun turret, and did not cope well with the extra weight as a result), and the ammunition was really, really subpar.
 
Why do you keep insinuating that I think the US 75 is tHe BeStEsT gUn EvAr. Its not so stop trying to be coy about it with the snide comments. We don't know what effect the War will have, we don't know what the fall of France will cost the UK's armoured forces or if there will be a panic which slams the brakes on any development for stuff needed NOW.
I'm a bloody Brit so I don't think that the Sherman is the be all and end all either so none of that crap either.

But, what I think is that the 6lber will be with British forces for longer than you're predicting, mainly because the pressures of war will mean that any switch over to producing the Valiant replacement will take longer and it'll be more towards 43/44 by the time its ready without it being rushed. Yes they're looking at it now, but they've not got the hull that can carry it yet. Until they do, you've got to use the 6lb gun. And even if you fiddled with its HE shell to make it more effective its still a 57mm shell. The rebored 6lb fiting the 75mm is a superior HE and infantry supporting weapon, we know this from WW2, sure its not as good an AT weapon, but its still adequate until the Tiger and Panther come along whilst the 6lb will do better against those tanks with better ammo.

Im a Brit as well, im also fully aware of the flaws of British tank doctrine and arms. If given the choice between the 6pdr and the 75mm I would choose the 75mm from the outset. I have never claimed the 75mm was a bad gun, I have taken exception to the attitudes of some members of this forum in trying to make the US 75mm a thing before it is realistic or practical.
The thing isn't as much as the ROQF was a useful gun for Britain in Normandy that gave very good service it was a cludge. Britain only went with it because the vickers 75mm HV wouldn't fit in the Cromwell. So despite using the 75mm for over 18 months Britain only went with it as a last resort. TTL the situation is completely different, the replacement gun is already in the works and the replacement tank not far behind (remember Carden did a little bit of work on a big tank that can take a bigger gun but stopped to focus on the design that firlts the railway loading gauge).
Right now Britain hasn't even gone to war, who knows how the war will progress much beyond the fall of France. All we know is Britain has a good tank with the possibility of a decent gun in the 6pdr on the way. It also has an excellent gun in the works. Britain may not even use many American tanks in combat due to greater availability of home grown designs and the resultant easier logistics.
There is also the possibility that the US 75mm never sees service. America was willing to adopt British guns way war as seen by them adopting the 6pdr. If given the option I could well see them putting the new vickers gun in the Sherman rather than the 75mm. Its likely got a comparable HE whilst having much better AP. Its also likely going to be designed and in production before the sherman enters production so it won't be a massive burden.
 
I agree that US 75mm lovies assumptions that its a great tank gun are seriously overstated.

There is a different timeline in play here. Carden is looking at a 3" gun for probably the Valiant follow-on, so by the end of 38 he will know what size turret is needed - the 3 man turret is already seen as the ideal, and I don't see him designing a new tank that can only take 2 men. Obviously he will apply any tricks used by the new 6pdr that reduce recoil and space, but they will know the space requirements.
The gun will likely be developed in parallel with the 6pdr (which will fit in the Valiant 1), so at the very least its available in 41 as an AT gun. And while there may not be orders yet, I certainly expect a Valiant 2 to have a demo/test model, once the tankies demand better it's all ready to go into production. When its demanded will depend a lot on how long the fighting in NA lasts. There is also the issue of when the British find out the Germans are designing Tigers and Panthers; when they do, the Valiant 2 is the obvious answer.

Now the Sherman isn't even on the drawing board yet. When this comes to pass, they need a gun. They can use a venerable old French design (which has a low mv), or they can develop a better version themselves (which takes time) or license the state-of-the-art British design. Which can still, if you want, handle a low mv/high HE charge shell if that's what you want, but can also punch holes. Possibly, given the US doctrine on tank destroyers, the same gun in tanks and TD, but a lower velocity shell in the tanks. It still has the advantage your only building one gun, with minor ammo differences. A big plus for the US way of making war material.
Its quite likely the US also develops their own better 75mm gun (they have the resources), but if they do its logical (doesn't mean that it will happen of course!) to make it so it too will fit their TD and tanks, giving them another option.
 
The americans could do more infantry carriers and stuff instead for the british or build even more trucks and stuff like that wich the british probably wouldnt mind taking?

And i think that is a thing a u might try to promote for the lesser firms in the heavier engineering firms, instead of tanks make bren carriers i think or its equlievants instead of forcing them into tanks ? Or armored cars and big trucks .

As astro said , the 77mm (3incher) will probably be a AT gun in 41 and i dont advocate doing it for the valiant like some people are but for the follow up tank instead in 42/43 and be the main tank for d-day onwards.
 
The Americans refused point-blank to accept the 76mm in the modified M4 turret, and it wasn't until someone had the bright idea of mounting the T23 turret that they finally accepted it,
but postwar, the Military Assistance Program took 75mm armed Shermans, an replaced the 75mm with the 76mm, along with other minor upgrades like the direct vision Cupola. Yugoslavia ended up with a number of these, along with other Western leaning governments.

It had some of the downsides as the Firefly, but would have been very servicable, and honestly, should have been done.
That way it could have been found that it wasn't the wonder weapon that Ordnance claimed it would be, when put into combat in 1943 rather than 1944
 
A high velocity 6 pdr could have been a choice for Shermans.

As it worked out, the last Shermans in actual Military Service, had OTO-Melara 60mm guns in ex-Israeli M50 Sherman tanks
1606656797816.jpeg

this is a 70 caliber long tube and had APFSDS 1620 meters per second
1606656966604.jpeg

and HE.

Last ones in Chile were retired in 2003
 
The 60 mm HVMS was designed specifically to put that APFSDS dart through the front plate of a T-62 at 2,000 meters. It would require advanced metallurgy impossible for the time to withstand the chamber pressure necessary for that. By the standards of the time, the 30-ton Sherman was undergunned for its size when it emerged with the 75 x 350R gun. The problem for the Americans at the time was that there was nothing between the 75 and the 3-inch gun, which was too large and heavy for a fully armored 30-ton tank.
 
And ITTL they're likely to be much less pressed for equipment, and the equipment on offer is better.


The war office might, but the war office hasn't put out a specification for anything even close to that yet, and Carden seems more inclined to consider actual combat effectiveness of the crew.


One thing the British never prepared for was enemy AT guns.


'Moving away from' a vehicle takes time. And even when the vehicle is out of production, replacement parts will be coming down the line until all the vehicles in service have been replaced. I wouldn't be especially surprised to still bee the Valiant I in use by whatever is this timeline's equivalent of D-Day.


The Americans refused point-blank to accept the 76mm in the modified M4 turret, and it wasn't until someone had the bright idea of mounting the T23 turret that they finally accepted it, and even then, they had sufficient concerns that the initial idea of shifting all production to 76mm was reduced to one in three tanks being 76mm. That last one was probably a good idea, as the Germans produced a total of fewer than 8,000 heavy tanks (Panther, Tiger I, Tiger II), most of which ended up on the Eastern Front. And those are really the only targets against which a high velocity gun like the 76mm or 17 pounder excelled, against everything else, the Panzer IV, etc. The 75mm M3 worked perfectly adequately, and had the advantage that the HE shell could actually deal with the real danger to vehicles on the advance, Anti-tank guns.


You're making a big hoo-rah about this experimental Vickers design, yet you have no idea if it can even be fitted into the Valiant I (it probably can't, not without making unacceptable compromises). That being the case, the 75mm is a perfectly acceptable weapon, given that most of the targets these things are going to be facing are not tanks, and thus don't need the punch of even the 6-pounder to kill.

1, The fact Britain is likely going to be in a much better position regarding equipment means they are likely to rely far less heavily on American equipment. That means less exposure to the 75mm.

2, True, any requirement for fitting the Vickers into a tank is a long way off. Any requirement for a MV 75mm gun however is even further off. Also just because the requirement for the new vickers gun does not exist yet does not mean Carden won't look at pre empting it.

3, Carden is TTL. That's why he asked for a great HE round as well as great AP round. You are right about Britain neglecting HE capabilities for tank guns OTL. Why would TTL be any different?

4, Agree but what role the vehicle is in will depend. I doubt it will be still in use as a front line tank.

5, how the Americans acted during the war does not necessarily indicate what they will do pre war. If Britain asks for modifications to the turret so it can take the Vickers HV then I would expect the Americans to at least listen and consider. At this point the British are the ones with all the war experience.

You're right again that in order to fit the new Vickets HV into the Valiant will likely require compromise. The thing is Britain was always perfectly willing to make those sacrifices.
I have also never claimed, or at least never intended to claim that the 75mm was a bad weapon. It wasn't. What I have claimed is that the drivers that saw the ROQF adopted OTL won't exist or will be reduced TTL. That in my opinion makes it's adoption unlikely at best and a complete non starter at worst.

Let's not forget the ROQF 75mm was only adopted OTL because the Vickers 75mm HV wouldn't have fit into the Cromwell turret.
 
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