jackssmirkingrevenge wrote:let's take for example the US Army's, solution to the problem, the
M829 kinetic energy penetrator - that leaves the barrel at over 5 times the speed of sound with a whopping
4,391,500 ft/lbs 
Pittance.
The
Maxwell Labs' Railgun throws a 1.6kg (3.5 lb) projectile at 3300m/s (10830 fps, roughly Mach 10), for
6,429,520 ft lbs of energy - at a decent (for a railgun) 27% efficency.
Of course, it's not pratical as an anti-tank weapon yet, but it shows what the future could be like.
Those DU rounds are pretty hefty. Having been part of the Army cadets (Royal Artillery), I've been shown the typical anti-tank rounds, including a APFSDS DU round (not sure what exact variant).
The thing that strikes you about all the (non-explosive) rounds is just how much they all weigh. You look at the tungsten steel one, think "That can't be that heavy", then when it's passed to you, you nearly drop the thing - because it weighs more than twice what you think it does.
@goathunter: The DU round wasn't anywhere near 41 lbs in weight. As a rough guess, it was 10-12lbs tops.
Are you sure that 41 lb number doesn't include the propellant charge?