Originally posted by Maverick:
Actually the tank "destroyers" were gunned the same or used a 105 mm HOWITZER gun. They were considered much less capable than tanks as the howitzer is a slower velocity higher trajectory round than the 90 mm main tank gun later in the war. The other problem with the tank "destroyer" was the lack of ANY top cover. The turret was open to the sky. Any artillery with airburst could and did kill the crew in those vehicles.
American armor had only one advantage over later Geman tanks and that was in speed and mobility. The Soviets were in the same boat and that is why they did the best when they could close and mingle inside the German armor fomations. This made the Germans have to risk shooting each other and gave the lesser gunned allied tanks have the chance to hit the German tanks in the "ass" where the armor could be penetrated by 75mm guns. It's also much easier to immobilize a tank, instead of killing it outright, by damaging the treads. Those are more vulnerable to hits from the sides. Once a tank is immobilized the infantry will swarm it and kill it. A tankers greatest threat, outside of another tank, is infantry. That is why you do not see "pure armor" operations. They have infantry to protect the tanks from other infantry. Pesky little buggers. 
Mav
Okay I have to pick through this...
the original US TD would be the M10 Wolverine, a modified Sherman hull with an open-topped turrent and a gun that would become the main US AT gun in the later part of the war, the 76L64. Eventually the M36 Jackson came along, with the 90L50 gun, which was capable of defeating nearly all German armor. There was also the Archilles, an M10 with a 17pdr rather then the 76L64, and the M18, a high speed light tank with the 76mm.
It is not that these TD's were incapable of killing tanks, but they have very little armor and open tops, so killing a tank before being knocked out was a great challange.
The only two tanks I know of that the Americans had with a 105mm guns are the Sherman 105, and the M7 Priest. The M7's 105 was basicly field artillary support, while the Sherman 105 (M4 chassy with increased armor) was capable of carrying HEAT rounds that were moderately effect against medium tanks. A Sherman 105 was to avoid tanks if possible however, and serve rather to help infantry break through defened positions.
By the time the US was moving inland from the Normandy invasions, there were at least some 76mm equipped tanks, namely the M4A3-76, M4A3E2-76, and later on the M4A3E8-76, most of which were field modifications to the turrent to accept the new gun. Alas, the upped-gunned Shermans were mostly the platoon leader's, leaving the rest with the pityful M4A3's 75mm gun.
On to the Soviets. The whole reason German developed heavy tanks were because of engagements with superior Soviet tanks earlier in the war. When the Kv class was first encountered, the Germans had no tank that could knock it out, and it's involvment is responsible for the Tiger's development.
Later the T-34 was running circles around the German armor, and deflecting their shots just as easily...the Panther design is based around what they learned from the T-34 design. The later into the war, the heavier the Soviet tanks get. The T-34/85, Kv-85, Su-85, IS-1, IS-2, IS-3, Su-100, and Su-122 were all very capable of engageing any heavy German iron they encountered.
Last thing, there were plenty of "pure armor" engagments. Many occured on the Eastern front, Kursk being the biggest, plenty in North Africa, and the US had plenty were is was two or three heavy German tanks vs many more lighter US medium tanks.
- Jig
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Sorry, I can't stand speculation

[This message has been edited by Jigster (edited 07-30-2000).]