Here's a bit more about the problems with the Sherman and how they could have been fixed:
“Sir!”, Howard said, again giving their palm-forward salute. “If you would direct your attention to those derelict tanks over there, we will begin by demonstrating some captured German weaponry.”
The rusting hulks of three derelict early production M4 Shermans had been towed to the end of a firing range. Their narrow tracks had cut deep swathes scarring the verdant loam, and they were sunk to their bellies in the sodden turf. Five hundred yards away, at the near end of the field, stood the tall, sinister, unmistakable profile of an 8.8 cm Flugzeugabwehr-Kanone “Flak” 41 dual purpose gun, commonly referred to by the Allies simply as the dread “eighty-eight”, captured by the Brits in Tunesia. Emplaced adjacent to it was its little cousin, the Pak 40 anti-tank gun, its shorter, angled shield juxtaposed with the eighty-eight’s taller, wider shield conjuring up images of a ferret standing next to a mastiff.
At Howard’s signal, the ordinance crew chief shouted “fire in the hole,” and brought down his arm. The crew turned their faces away, covering their ears, as the gunner pulled the lanyard. As the eighty-eight recoiled, its shell screamed down range at 3,280 feet per second, more than 1,400 feet per second faster than a round from the Sherman’s 75mm main gun.
Sparks shot thirty feet in the air as the shell hit the frontal armor of the Sherman, penetrating it like a knife through hot butter. Sharp eyed observers noticed a second burst of sparks a microsecond later as the shell exited through the rear armor of the Sherman and buried itself in the wet turf.
“Field Marshal Slim,” Howard continued, “the Bosche have mounted an eighty-eight on their Tiger tanks, and they can knock out our Shermans from 1,000 yards. The Panther is armed with a 7.5 cm long barreled main gun, which, with a muzzle velocity of 3070 feet per second and flat trajectory, has even greater penetrating power. Note the effect of a shell from a similar 7.5 cm Pak 40 antitank gun,” nodding to the ordinance crew.
The smaller, more easily disguised canon fired, its shell less dramatically but equally effectively penetrating the derelict Sherman’s inadequate armor.
“As you are aware, Sir, both the Tiger and the Panther have far more effective armor, both thicker, and in the case of the Panther, sloped, making them more difficult to penetrate than the Armor of a Sherman. Please watch the effect of a shell from a Sherman armored with a short-barreled M2 75mm 31.5 caliber main gun with a muzzle velocity of 1850 feet per second.”
Howard waived to a 4th Light Horse crew in a running M4A1 Sherman. The commander’s body jerked as he gently kicked the right shoulder of his driver, who turned the tank to the right, pulled it to the beginning of the range, and stopped. The tank commander gave the verbal command “load armor piercing”, the loader rammed a shell home, the turret turned slightly, and the main gun elevated. At the command “Fire!”, the entire tank rocked backwards with the recoil, and the shell, which unlike the far faster German shells, was visible to the naked eye, arched down range to the target. At a little more than 500 yards, the shell ricocheted off the frontal armor of the derelict Sherman with a resounding metallic clang.
“Our 75mm shells will fail to penetrate the frontal armor of a Tiger or a Panther at even point blank range. Field Marshal, your British ordinance experts have managed to mount a 17 pounder anti-tank gun in the turret of a Sherman tank, creating the Firefly variant,” Howard said, pointing towards the tanks of his platoon. The 17 pounder has a muzzle velocity of 3,950 feet per second, and can penetrate 135mm of armor at 1,800 meters. Sir, if you would again focus your attention down the range,” Howard said, signaling to one of the tanks in his platoon.
The modified Firefly, whose tracks were nearly twice as wide, and which was equipped with thin metal side skirts similar to those I had seen on the Panzer IV’s I had encountered on the Biazza ridge, started forward, turned, and came to a stop fully 250 feet short of the beginning of the range. Its main gun, twice as long as the main gun on the ordinary Sherman, fired, flames bursting out the front and the two holes in its unusual, globular, muzzle break as the tank rocked violently from the recoil. Its armor piercing shell ripped through the Sherman like a rock through a plate glass window, then tore through the rear, sparks flying forty feet in the air each time.
“The Yanks have a 90mm gun mounted in their new M36 ‘Slugger’ tank destroyers, with a muzzle velocity of 2,800 feet per second which, while not quite as good, with American industrial might, could be mounted on Shermans in far greater numbers.”
“Sir, right now there is one Firefly for every troop of ordinary Sherman tanks in commonwealth armored divisions. The Yanks completely lack a tank with adequate firepower. Field Marshal, if every other tank were armed with a gun adequate to engage the heavier German tanks we will be facing, a lot more of these men will get home to Oz.”
Field Marshal Slim, obviously impressed, nodded, and enquired, “but what about these other modifications, the wider tracks and the side skirts?”
“Sir, the Sherman weighs 37-1/2 tons, and its tracks exert a ground pressure of over 14 pounds per square inch. The earlier Shermans, many of which are still in service, are equipped with a Continental R975C1 radial engine with 400 hp, providing a power to weight ration of ten horsepower per ton. The M4A3 substitutes a 500HP Ford GAA V-8, which is lower, more powerful and less finicky than the Continental radial. This provides for excellent mobility on the road, but the narrow tracks bear more weight per square inch than the much heavier seventy-ton Tiger and forty-eight ton Panther tanks, so the Sherman has very poor off-road performance, often bogging down. These tanks are fitted with track extenders, called “duckbills” which add about four inches to the track’s width. The tanks still lack the off-road traction of the German tanks, but at least with the track extenders there is some improvement."
