Members of the Free Syrian Army allegedly destroy an occupied Syrian Arab Army tank by sliding a hand grenade down the barrel, effectively rendering the vehicle useless.
This footage is a bit older, and it comes out of Syria. It shows members of the Free Syrian Army destroying a tank that they want the viewer to believe is occupied by Syrian Arab Army tankers. Upon further inspection however, it appears as if the tank was already disabled and abandoned by its previous crew. Regardless, this footage did still gain the FSA fighters a bit of knowledge about how to defeat SAA tanks, which were a system that at the time they had no reliable means of defeating.
This was recorded at a time before the Free Syrian Army was being supplied Anti-Tank Guided Missile systems by the Central Intelligence Agency. The only way they had to defeat SAA tanks before the CIA stepped in was by forming hunter-killer groups with RPGs, and attempting to ambush or disable the tanks before the tanks could tear them to shreds. At this point in the Syrian Civil War, it's important to note just how much of the fighting was taking place in busy urban environments where it was easy to isolate a tank without infantry support.
So, what the FSA fighters learned with this little test is that they could utilize hand grenades to cause a sympathetic detonation inside of the tank's main gun compartment, which would ultimately lead to not only the destruction of the tank, but also of its crew should they be able to get close enough to conduct the maneuver. We did not ever see any other footage of this technique being used on an active tank though, as shortly after it was filmed the 13th Coastal Division and Abu TOW started destroying SAA armor at the cyclic rate.