I'm not to convinced that modern armour like m1a2, challenger and leopard are that easy to knock out with modern tank guns. There are reports of friendly fire accidents where m1a2 DU rounds were unable to penatrate m1a2 armour. There is also a story of an m1a2 being stuck in the mud, and another m1a2 got the order to destroy it, but wasn't able to fully do so from close range.
There was also a challenger being hit by a hellfire in the side and yet the tank was disabled, the crew survived.
Fact is we know shit about modern armour and the effects modern weapons has on it. They still keep it pretty secret
But the thing is, I seriously doubt that insurgents could get their hands on tungsten or DU sabots and without those you don't stand a chance against modern tanks

As was proven in the first gulfwar. The iraqi t-72's had a good gun, but no tungsten rounds, they used hardened steel sabots, which even at close range couldn't do a thing against the m1a1 and challenger. While the DU sabots of the m1a1 even got kills over 2 km away and a challenger made a kill at 5km even
