The best candidate for a US heavy tank was the M6A1. The first of four pilot models was first completed days after Pearl Harbor. The M6A1 had a maximum armor thickness of 100mm and was armed with the 3" AA gun and a 37mm in the turret. The 3" gun had better armor penetration than the 76mm later added to US vehicles. The M6A1 was envisaged to enter service summer '42, just after the Sherman.
The M6 was a big, slow, beast. Plus, it had a higher silhouette than the M3. But it packed a wallop with the 3" gun. The M6 would have entered service ahead of the Tiger, giving it the biggest gun then in service. The 3" gun would have been a Tiger tamer, capable of kills on par with the 17pounder. Also, the enlarged turret, built to contain a 37mm also, could have easily been modified to accept the 90mm later on by simply deleting the 37mm.
The Army was nonplussed by the M6A1 because of its size and flawed US doctrine. The US at this time believed the best way to kill a tank was with a Tank Destroyer, a light AFV armed with a big gun, not with a tank. The M10 Tank Destroyer was already in service armed with the 3" gun. That and the fact that the M6 used aircraft engines that were desperately needed, doomed it. It was decided that between the M4, M10, and upcoming M18 TD, the M6 would not be needed. The initial order of 5,000 was reduced to 115 in March '42. Only 40 were eventually built though, the first production models arriving in September '42, they slowly kept completing M6's with parts produced in '42 and built the 40th and last one in Feb '44.
Not one ever saw combat. The M6's were used as training vehicles, and never fired a shot in anger. They did prove useful as test bed vehicles for eletric transmissions and the 90mm gun. The M6 came close to combat in July of '44. The Shermans were having such a terrible time in Europe that the M6A2 was built, this model sported a 105mm high velocity gun. One was converted in the States and 15 other M6A1's were packed to be sent to England and converted there. They got as far as the boat, when the German disaster at Falaise Gap happened at which time they were unpacked.
I have always thought that although a large, slow and ponderous vehicle that would have cost many aircraft early in the war, the M6 would have come in handy when the Panthers and Tigers rolled into town. Had they only produced 2-300 of them, and upgunned survivors to 90mm guns in '43.

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"The 3" gun had better armor penetration than the 76mm later added to US vehicles."

I don't know where you got this, but according to my sources the 76mm WAS the 3" gun. The 3" L/53 M5, M7 is exactly the same thing as the 76mm L/55 M1 etc. As for Tiger-killer, possibly under 500m with normal ammunition. With extremely rare APCR it could go out to 1500m.

BTW, all German guns of 75mm plus would be able to penetrate the M6 at 1500m too, at a pinch in some cases, but it would be theoretically possible.

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„Solange man nicht mit dem Kopf unterm Arm rumläuft geht es doch noch!" Erwin Rommel

Which is why the Shermans were nicknamed "The Ronson."

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Lost are only those, who abandon themselves) Hans-Ulrich Rudel.

The Ronson was a cigeratte lighter that always worked and everytime a sherman was hit it caught on fire.Hence they called it the Ronson because it never failed to light up.

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Different guns my friend. Often confused, but different. The 3" at close range had only slighty better punch than the 76mm, at longer ranges the 3" had a considerable more punch. The 3" was slightly longer, with a tighter "squeeze" at the muzzle increasing velocity. The 76mm is the same basic gun, tamed slightly to improve reliability.

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The best online source for gun information I have found is guns vs. armour by Claus B. He gets his information from a multitude of sources and claims that the penetration statistics of the 3" and the 76mm are exactly the same. Of course I'll give you the benefit of doubt.

Especially the fact that the 3" is an AA gun might mean it takes different ammo or is in fact a different gun. Are there maybe two different 3" guns?

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„Solange man nicht mit dem Kopf unterm Arm rumläuft geht es doch noch!" Erwin Rommel

In "Tanks WWII"by George Forty, Forty writes,"The 3" gun of the M18 Hellcat gave it superior firepower to even the 76mm armed Shermans as the 3" had much better long range punch"
In "Tanks of WWII" by Terry Gander, Gander writes,"The 3" AA gun was not mounted on any US tanks as it was believed barrel wear would be excessive, and tanks would be forced to constantly replace barrels.......the 3" fired a lighter projectile at higher velocity giving better performance at longer ranges"

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Okay, the site Guns vs Armour is currently down, so I can't access it.

So, a wild shot in the dark: [img]smile.gif[/img] Maybe APCR ammo was only issued to M18 Hellcats? And thus this misunderstanding that they had two completely different guns arose?

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„Solange man nicht mit dem Kopf unterm Arm rumläuft geht es doch noch!" Erwin Rommel

Anyways, What does anyone think about the M6 and its chances to alter the battlefield?

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It's a sick, sick world. I'm a happy man.

Not so good. Too slow, too big, too expensive and for that simply not good enough. Sure it packs a wallop and can take some punishment, but really I'd prefer to have a few more Shermans rather than an M6.

BTW, I have now found a page with gun statistics and the 3" and 76mm not only fire exactly the same ammo but also get exactly the same penetration!

Only the M7 3" gun apparently fires slightly advanced ammo (M79 AP) but the difference wasn't that big and the overall performance was nothing to oh and ah about.

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„Solange man nicht mit dem Kopf unterm Arm rumläuft geht es doch noch!" Erwin Rommel