This entity is 
not in the  
FGD by default.
It should not be put directly in a map because it can only be configured through code. 
 
grenade_tank_shell  is a   model entity  available in 
 Black Mesa. The grenade entity that used by npc_abrams. This is a projectile fired from the barrel of an Abrams tank. 
Bug:This grenade entity can stuck at dynamic (not physics) objects, such as prop_dynamic. In such situation, shell will not move until it explodes. Usually happens with objects that have a dynamic collision, or objects that are in motion.
Tip:If you need to fix this issue, use trigger_weaponfire that will kill stucked rockets, this trigger should be toggled by logic_timer every 0.5-1.0 seconds. 
Example.
| 
  
 
		
			
			
Example with this metal door. The door is prop_dynamic with dynamic collision (required for animations).
 
			 
		  
 
 | 
(not in 
 for grenade_abrams_shell)
 
Note:Used model from MP5's grenade model for some reason. 
Note:For some reason it's spinning. 
Note:It disappears if hits skybox. 
	
		| Cvar/Command | 
		Parameters or default value | 
		Descriptor | 
		Effect | 
	
		| sk_detenator_tank_shell_dmg | 
		40 | 
		Float
			 | 
		Amount of damage from this entity. | 
	
		| sk_detenator_tank_shell_radius | 
		256 | 
		Float
			 | 
		Radius of explosion from this entity. | 
	
		| sk_abrams_shell_speed | 
		2000 | 
		Float
			 | 
		Speed of this entity. |