Muzzle velocity is a factor of meters per second a round travels when it leaves the muzzle. This, of course, decreases as soon as the projectile leaves the tube. The size of the charge (powder in the casing in a tank round), length of the barrel, rifling, taper (if any) and quality of the propellent all determine muzzle velocity, not to mention temperature, all determine muzzle velocity.
Added to muzzle velocity is penetration. Obviously, mass and kenetic energy have a lot to do with this: Example, an 88mm round traveling at 3,000 feet per second will have a lot more penetration ability than a 37mm round at the same speed.... The 155mm HE rounds an artillery piece fires almost literally lob onto a target, but they'll go through a LOT of armor, just due to weight!
I don't have any reference material here, but at long ranges an 88 would retain more penetration ability than a 75 just due to mass.
All 'round, the Panther is acknowledged as a better tank than the Tiger I (and M26 I believe). Power to weight was better, reliability was better and armor disposition was better. Its gun couldn't 'reach out and touch' someone as well as the 88, but all in all, I'd take a Panther over a Tiger, if I were a German tanker.
If I remember, I'll take a look at some specs for the 75 and 88 tonight, as well as the 90 on the Pershing. Also, if I'm not mistaken, the 75, 88 and 90 were all better than the early JS series 120mm (it was a 120, wasn't it?) due to quality of propellent.
Any help from y'all who know more about German armor?
Ron.
I also heard that Ordnance told Eisenhower (before D-Day) that the 76 on the Sherman could take care of a Panther.... I'm sure some Colonel or General at Aberdeen was fried for that one!