When the 120 mm gun of the M2A1 Slammer is fired, the recoil pushes it so far back into the turret, that the bore evacuator (the cylindrical device mounted on the gun) is pushed back into the turret.
While there are recoil compensators on most tank's main guns, they don't allow for that much movement. The Merkava Mk IV's main gun recoils up to a maximum of 400 mm. Ingame it seems to be much more.