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Have you looked at the amount of craft work required to convert a Sherman tank into a Sherman Firefly? I am unable to find a historical price but I suspect the conversion cost as much as the original tank.British had one modification of the existing tank that cost them almost nothing, that being Sherman Firefly.
The Vickers 75mm HV was supposed to fit in the new Cromwell tank, but it was discovered rather late in the day that the Cromwell's turret was too small, causing a major crisis.
...meaning the HE round was notably better for the 75mm HV. It was also better than of the 17pdr, HE round featured the thick-walled shell there. 17pdr is far better AP thing, unsurprisingly.The M61 [APCBC projectile]weighed 6.77 kg and was fired at 808 m/s from the Vickers HV for a muzzle energy of 2,200 kJ, compared with 620 m/s from the US tank guns (1,300 kJ). As a result, penetration went up from about 60mm to an estimated 87mm - not a huge amount more than the 6 pdr 7 cwt, but with a vastly more effective HE shell. The M48 [HE round] was downloaded to only 457 m/s since the thin-walled shell could not take the same high chamber pressures as the M61.
(the 76mm M42 HE shell contained only 390g TNT compared with 667g for the 75mm M48)
Meanwhile, Vickers persevered with their 75mm HV and the next tank, the Comet, was designed around it to make certain that it would fit this time! Before it could enter service, it was decided to take the calibre back up to the original 76.2mm so that the new gun could use the same projectiles as the 17 pdr, and the gun was then renamed the 77mm (presumably to distinguish it from the US 76mm).
the 77mm with this ammo [APDS] could penetrate 165mm [range not stated, 100 yds maybe?]
I don't think that anyone is trying to blame the British for fielding the 17pdr.
As for German AT guns heavier than the 'regular' 7,5cm pak, all of them were requiring the good vehicle to tow them. Going for the SP version makes far more sense to me.
The 77mm is a version of the Vickers 75mm HV that was intended to be the Cromwell's normal gun. Due to some **** up in coordination they then found it wouldn't fit! Hence the panic to try to get a 17 pounder into something. The Comet was designed around the 75mmHV that used the 3" AA case but reverted to the 3" (76.2mm) bore but was termed 77mm to avoid confusion with other 76mm rounds.
The 17 pounder was a next generation tank gun and really demanded a next generation tank (Centurion). The 77mm,, nee 75mmHV, was the intended 1943/4 intermediate gun. In it's absence, and in the knowledge that a 6 pounder APDS was a viable (if not ideal) anti tank gun, I wondered if it could fill the gap with a little tweaking.
If the Vickers 75mmHV had fitted then the Cromwell (and presumably Churchill) would have been quite formidable machines in 1944.
Yep, the Comet/Cromwell look like having a gun 'inside' the tank, while the Sherman looks like the gun is 'outside' of the tank.The external mantlet of the Sherman left less 17 pounder protruding into the turret than in a Cromwell/Churchill type of turret with an internal mantlet. Even then it had to be mounted on it's side and substantially modified. Put one in a Cromwell and the breech hits the turret rear if it fired. The good news is that it would have too little room left in the turret to load a 17 pounder round anyway.....
I heard a (very) dubious story that someone at the time asked if a 17 pounder could be put into a Grant as there was more room inside, the turret be removed and additional armour added.
Roger that.It is not you but somebody on this thread is trying to make out like it was a mistake.
Very true, once you are above the size of the 50mm Pak or perhaps the 6pdr manhandling the guns any distance beyond a few hundred yds is impractical. However towed guns are cheap. A towed gun may cost 10% of what the similar gun in a tank would cost and trucks are no where near as expensive as any sort of track laying vehicle.
the 77mm with this ammo [APDS] could penetrate 165mm [range not stated, 100 yds maybe?]